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A  TOPICAL 


SYNOPSIS  OF  LECTURES 


ON 


ANIMAL  PHYSIOLOGY. 


BY 


HENRY  SEWALL,  PH.  D„ 

PROFESSOR  OF  PHYSIOLOGY  IN  THE  UNIVERSITY  OF  MICHIGAN. 


SECOND  EDITION  REVISED. 


ANN  akbor: 

THE   REGISTER   PRINTING  AND   PUBLISHING  HOUSE, 
1885. 


aT'4 


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AUTHOR'S  NOTE  TO  THE  FIRST  EDITION, 


This  skeleton  of  a  course  of  lectures  on  physiology  has  been 
-prepared  at  intervals,  with  the  sole  object  of  helping  students  to  fix 
the  attention  upon  the  main  facts  of  the  subject.  The  topics  have 
served  simply  as  points  of  departure  in  the  lecture  room,  and  no 
effort  has  been  made  to  render  the  "  Synopsis  "  clear  to  any  for 
whom  the  spaces  between  the  paragraphs  have  not  already  been 
filled  in.  The  author  has  been  burdened  with  no^desire  for  origin- 
ality, and  for  good  reasons  the  admirable  text-books  of  Professor 
Martin  and  of  Dr.  Foster,  especially  the  latter,  hgve  frequently  been 
followed  in  l»oth  order  ,and  substance  in  the  preparation  of  these 
notes. 


I.    THE  OBJECT  OF  PHYSIOLOGY  AND  THE:F0NCTI0NS  OF  LIVING 

MATTER. 

Pliysiology  is  the  study  of  the  chemistry  and  physics  of  the 
liviug  body. 

Physiologically,  Life  is  the  smu  of  the  functions  of  matter 
called  Protoplasm. 

Protoplasm  is  made  up  of  the  elements  C,  H,  O,  N,  traces 
of  P  and  S;  some  inorganic  salts.  Contains  much  water  and 
probably  residues  of  proteids,  fats  and  carbohydrates. 

To  make  protoplasm  needs  building  material  and  building 
energy. 

In  the  animal  both  are  supplied  by  the  food  and  oxygen 
taken  in. 

In  the  green  plant  sunlight  supplies  building  energy. 

Living  protoplasm  is  continually  wasting. 

In  the  animal  the  waste  matter  contains  less  potential 
energy  than  the  food;  the  energy  difference  is  the  vital  force 
of  the  animal. 

The  general  functions  of  all  protoplasm  are  exhibited  by  the 
simplest  living  thing,  as  an  amceba,  or  ivhiie  blood  corpuscle. 

These  functions  are: 

Contraciiliiy. 

SpontaneUy. 

Irriiabiliiy. 

Conductivity. 

Co-or  dined  ion. 

Assimilation.  This  leads  to  Growth  by  Intussusception. 
Growth  stops  when  the  weight  of  egesta  equals  that  of 
in</esta.  As  the  amount  of  waste  matter  depends  upon 
the  mass  of  protoplasm  and  the  amount  of  matter  assimi- 
lated upon  its  surface,  growth  must  have  its  limit  accord- 
ing to  the  law  of  unequal  increase  of  mass  and  surface. 


-6— 

Reprodudion. 

The  highest  animal  exists  first  as  an  egg,  a  single  cell. 

Multiplication  of  cells  hy  fission. 

The  body  is  composed  of  cells,  modified  cells  and  intercel- 
lular matter. 

Differentiation  of  tissues. 

Physiological  division  of  labor.    . 

Physiological  classification  of  tissues  into: — 

Undiffei  ■eniiaied. 

Supporting. 

Nidriiive;  including  assimilaiive;  secreiory;  receptive;  elim- 
inative;  respircdory;  meiaholic. 

Storage. 

Irritable. 

Conductive. 

Co-ordinating  and  Automaiic. 

Motor.  * 

Protective. 

Reproductive. 

II.    THE  NATURE  OF  THE  LAWS  SUPPOSED  TO  RULE  THE  ACTIY- 
rriES  OF  THE  BODY. 

The  physiologist  studies  vitality  as  a  manifestation  of 
chemical  and  physical  energj'  and  believes  the  laws  governing 
living  and  not  living  things  to  be  equally  inflexible. 

Energy  exists  in  two  states,  Poteidial  and  Actiifd  or  Kinetic. 

Potential  energy;  represented  in  the  position  of  masses;  by 
position  of  atoms  in  molecules. 

Kinetic  energy;  represented  in  the  motion  of  masses  and 
of  molecules  and  atoms. 

The  different  kinds  of  energy. 

One  kind  of  energy  may  be  changed  into  another. 

Energy  is  indestructible. 

Energy  cannot  be  created. 

The  uses  of  a  machine  as  illustrated  by  the  steam  engine, 
the  pulley  and  the  watch  springy 


— 7— 

The  principle  of  the  dissipation  of  energy. 
Consider  the  whole  history  of  the  energy  represented  in  a 
stone  thrown  by  the  arm  into  the  air. 

Ill,    THE  LYMPH  AND  BLOOD. 

The  linid  parts  consist  of  t^od  matters  dissolved  and 
altered  by  digestion  and  the  activity  of  metabolic  tissues,  and 
of  the  products  of  tissue  change. 

LYMPH. 

The  tissue  elements  are  bathed  in  lymph. 

Physical  and  chemical  characters  of  lymj)!!.  Lymph  cor- 
puscles. 

Lymph  derived  from  blood  by  diffusion. 

Nature  of  diffusion;  inffuence  of  temperature;  of  the  divid- 
ing membrane;  of  the  concentration  and  composition  of  the 
diff'using  fluids. 

Effect  of  blood  pressure  on  the  diff'usiou  from  the  blood 
vessels.     The  use  of  the  lymphatics  as  drainage  vessels. 

Various  directions  of  the  lymph  currents  of  dift'usion  in  the 
hodj. 

Influence  of  the  blood  circulation  on  the  rate  of  dift'usion  by 
the  supply  of  new  and  removal  of  waste  matter. 

Physical  and  vital  characters  of  lymph  corpuscles. 

Coagulation  of  lymph. 

BLOOD. 

Consists  physically  of  straw-colored  iiuid  plasma  and  of 
solid  red  and  white  corpuscles. 

Relative  number  of  red  and  white  corpuscles.  Conditions 
of  its  physiological  variation. 

Size,  shape,  physical  and  vital  characters  of  white  cor- 
puscles. 

Number,  size,  shape,  physical  characters  and  function  of 
human  red  corpuscles. 

Distinction  between  the  red  corpuscles  of  mammals  and  of 
other  vertebrates. 


— 8— 

Rouleaux  of  red  corpuscles  in  drawn  blood. 
Stroma  and  lisemoglobin  of  red  corpuscles. 
Cause  of  opacity  of  blood.     "Laky"  blood  and  means  of 
producing  it. 

Composition  of  lisemoglobin;  lisemoglobin  crystals. 
Characters  and  production  of  haemin  crystals. 
The  colorless  "blood-plates"  of  Bizzozero. 

COAGULATION  OF  BLOOD. 

Physical  changes  in  blood  on  coagulating;  jelly  stage;  solid 
clot;  cupping;  serum;  "resolution"  of  clot. 

Demonstration  of  fibrin  threads  in  the  clot  produced  on  a 
microscope  slide. 

Phenomena  of  clotting  in  a  capillary  tube. 
Effect  of  whipping  fresh  blood. 

(  Plasma. 
Before  clotting  < 

I  Corpuscles. 
Physical  components  of  blood 

(  Clot=fibrin+ 
After   clotting  <      corpuscles. 
(  Serum. 

Whipped  blood=corpusclesf  serum. 

Red  corpuscles  have  nothing  to  do  with  coagulation. 

The  hvffy  coat;  its  nature  and  conditions  of  occurrence. 

The  reason  for  its  occurrence  in  blood  in  inflammatory  dis- 
ease. 

Relation  of  the  shape  of  the  clot  to  that  of  the  containing 
vessel. 

Color  of  clot  at  different  distances  from  the  free  surface. 

Uses  of  clotting  to  a  wounded  animal. 

Fibrin  does  not  exist  as  such  in  normal  blood. 

CAUSES  OF  COAGULATION  AND   INFLUENCES  MODI- 
FYING IT. 

Old  theories  that  clotting  was  due  to  escape  of  ammonia ; 
to  taking  up  of  oxygen. 

Significance  of  blood  clotting  under  mercury. 


Views  that  clottiiif];  was  due  to  loss  of  heat;  to  cessation  of 
circulation. 

Hypothesis  that  the  internal  coats  of  the  blood  vessels  pre- 
vent coagulation. 

Evidence  as  to  intinence  of  internal  coat. 

View  that  blood  does  not  tend  to  clot  until  chemically 
altered. 

Influence  on  coagulation  of  temperature;  of  strong  solu- 
tions of  mineral  salts;  of  stirring. 

White  blood  corpuscles  always  found  in  spontaneously 
coagulating  fluids. 

The  deposit  of  fibrin  around  a  foreign  object  in  flowing 
blood  is  preceded  by  accumulation  of  white  corpuscles. 

In  the  thin  clot  upon  a  microscope  slide  the  fibrin  threads 
start  from  white  corpuscles. 

In  slowly  clottiijg  horse's  blood  the  firmest  clot  is  at  the 
level  of  greatest  accumulation  of  white  corpuscles. 

Direct  observation  under  the  microscope  of  thrombus  for- 
mation in  a  frog's  tongue. 

The  disintegration  of  white  corpuscles  and  transition 
forms  on  drawing  blood  from  the  body. 

All  that  has  here  been  said  of  the  white  corpuscles  prob- 
ably holds  true  for  the  colorlesss  "blood-plates." 

Denis'  plasmine. 

Clotting  of  the  solution  of  plasmine. 

The  blood-clot,  jibyin,  is  probably  formed  from  a  proteid 
body,  jihrinogen,  a  constituent  of  the  blood-plasma,  under  the 
action  of  a  fibrin-fcnncnt  which  is  produced  by  the  disinte- 
gration of  the  colorless  corpuscles  ( leucocytes  or  blood-plates, 
or  both. ) 

Fibrinogen  is  found  in  solution  in  transudation  fluids;  is 
precipitated  by  saturating  with  salines;  is  dissolved  by  dilute 
salines. 

Hastening  of  clotting  by  addition  of  fibrin-ferment  to 
diluted  plasma. 

Necessity  of  salines  to  coagulation. 


—10— 

The  action  of  the  fibrin  ferment. 

The  nature  of  animal  ferments;  conditions  of  action. 

The  origin  of  fibrin  ferment  and  method  of  obtaining  it. 

^  THE  TRANSFUSION  OF  BLOOD. 

Transfusion  as  practiced  on  the  isolated  hearts  of  the  frog 
and  dog. 

The  nature  of  the  foreign  blood  is  not  indifferent. 

Danger  in  direct  transfusion  of  clotting  in  the  transmission 
tube. 

Danger  of  injection  of  whipped  blood  because  of  its  con- 
tained fibrin  ferment. 

Experiments  illustrating  this  point. 

CHEMISTRY  OF  BLOOD. 

Average  specific  gravity  of  human,  blood  is  1055;  relative 
weight  of  corpuscles  and  plasma. 

Corpuscles  form  one-third  to  one-half  of  the  weight  of  the 
blood. 

Reaction  of  blood;  its  variation  in  clotting. 

The  amount  and  kinds  of  gas  given  off  in  vacuum  by  a  vol- 
ume of  blood;  by  serum. 

Chemical  composition  of  serum;  nature  of  its  solid  mat- 
ters. 

The  ash  of  serum  contrasted  with  the  ash  of  corpuscles. 

Chemical  composition  of  the  red  corpuscles;  of  the  white. 

HISTORY  OF  BLOOD  CORPUSCLES. 

Evidence  for  the  transitory  nature  of  the  corpuscles ;  varia- 
tion in  number  at  different  times;  probable  derivation  of 
urinary  and  bile  pigments;  normal  number  quickly  regained 
after  hemorrhage 

Origin  of  the  red  corpuscles  in  the  embryo;  metamori^ho- 
sis  of  mesoblastic  cells;  transformation  of  white  corpuscles 
arising  in  the  liver  and  spleen;  from  the  protoplasm  of  con- 
nective tissue  corpuscles. 


—11- 

Origiii  of  rod  corpuscles  in  the  adult;  raetanlori)li<)se(l  from 
transitional  forms  of  white  corpuscles  found  in  the  spleen  and 
red  medulla  of  bones. 

Fate  of  red  cor})uscles;  probably  destroyed  in  the  spleen. 

White  corpuscles;  physiological  variation  in  number. 
Arise  in  lymphatic  glands  and  similar  organs.  They  pi-ob- 
ably  serve  as  occasional  tissue  l)uilders,  and  give  rise  to  red 
corpuscles. 

THE   QUANTITY   AND    DISTRIBUTION  OF   BLOOD   IN 

BODY. 

About  one-thirteenth  of  liody  weight  is  blood;  of  this  is 
contained: 

One-fourth  in  heart,  lungs,  large  arteries  and  veins. 
One-fourth  in  the  liver. 
One-fourth  in  skeletal  muscles. 
One-fourth  in  the  remaining  organs. 

DEMONSTRATIONS. 

Whipped  beef's  blood. 

Laky  blood. 

Method  of  obtaining  hremin  crystals. 

Separation  of  corpuscles  and  plasma  in  horse's  blood  pre- 
vented from  clotting. 

The  clotting  of  plasma  from  horse's  blood. 

Plasmine  of  Denis. 

Clotted  horse's  blood  showing  buffy  coat. 

Clot  and  serum. 

The  phenomena  presented  in  the  clotting  of  freshly  drawn 
blood. 

Effect  of  whipping  freshly  drawn  blood;  character  of  the 
fibrin  obtained. 

The  clotting  of  blood  under  mercury. 

IV,    THE  CHEMISTRY  OF  ANIMAL  TISSUES. 

All  the  activities  of  the  body  are  due  in  the  end  to  chemi- 
cal processes. 


—12— 

The  body  is  composed  of  living  matter,  protoplasm,  and  of 
not  living  matter  which  is  made  by  protoplasm;  otherwise, 
the  body  is  composed  of  Formative  and  of  Formed  matter. 
In  general,  formative  matter  exists  in  cells  while  formed  mat- 
ter is  intercellular. 

The  molecule  of  protoplasm  contains  residues  of  proteids, 
fats,  and  carbohydrates,  besides  salines  and  extractives. 

PROTEIDS. 

These  form  the  principal  solids  of  active,  tissues,  of  blood 
and  of  lymph. 

The  molecule  is  very  complex;  composed  of  many  atoms  of 
O,  H,  N,  C,  with  S  and  P. 

Proteids  are  amorphous. 

All  are  non-diffusible  except  Peptones. 

Mostly  coagulated  by  alcohol  and  ether. 

Soluble  with  change  in  strong  acids  and  alkalis. 

Chemical  reactions;  xanthoproteic;  Millon's;  caustic  soda 
and  copjjer  sulphate,  etc. 

CLASSES  OF  PROTEIDS. 

1.  Native  albumins;  serum  and  egg  albumin.  Soluble  in 
water. 

2.  Derived  albumins  or  albuminates;  acid  and  alkali 
albumin;  casein.  Not  soluble  in  water  but  in  dilute  acids 
and  alkalis.  Not  precipitated  by  boiling.  All  proteids  dis- 
solved in  acid  or  alkali  bfecome  albuminates. 

3.  Globulius;  globulin;  paraglobulin ;  fibrinogen;  myosin. 
Not  soluble  in  water  but  in  dilute  salines;  precipitated  by 
strong  salines. 

4.  Fibrin.  Insoluble  in  water  and  dilute  salines.  Soluble 
with  difficulty  in  strong  salines  and  dilute  acids  and  alkalis. 

5.  Coagulated  proteids,  soluble  only  in  strong  acids  and 
alkalis. 

6.  Peptones.  Soluble  in  water.  Not  precipitated  by 
acids,  alkalis  or  boiling.  Diffusible.  Product  of  all  proteid 
digestion.     Many  varieties. 


— i3— 

KITROGENOUS  NON-CRYSTALLINE  BODIES  DERIVED 
FROM  AND  ALLIED  TO  PROTEIDS,  BUT  NOT  CAPA- 
BLE OF  REPLACING  PROTEIDS  IN  THE  FOOD. 

They  contain  the  elements  C,  H,  N,  O,  and  sometimes  S. 

Mucin;  a  secretion  of  mucous  epithelium. 

Chondrin;  the  organic  basis  of  cartilage.  Its  solutions  set 
on  cooling. 

Gelatin ;  organic  basis  of  bone,  teeth  and  tendon.  KSolutions 
set  on  cooling. 

Elastin;  from  elastic  tissue.     Its  solutions  do  not  gelatinize. 

Keratin;  from  hair;  nails;  epidermis. 

Nuclein ;  from  nuclei  of  pus  corpuscles. 

COMPLEX    NITROGENOUS    FATS  CHIEFLY    FORMING 
PARTS  OF  NERVE  TISSUES. 

Lecithin  (C^^HsoNPOs). 

Protogon. 

Cerebrin. 

STORE  MATERIALS  LAID  UP  IN  THE  BODY  AS  FOOD 
FOR  THE  TISSUES;  FATS,  AND  CARBOHYDRATES. 

FATS. 

Neutral  fats  are  compounds  of  a  fatty  acid  with  glycerin. 

They  are  made  up  of  the  elements  C,  H,  O. 

Insoluble  in  water.  Soluble  in  ether,  chloroform  and  hot 
alcohol. 

Are  decomposed  by  caustic  alkalis  forming  soaps  with 
them,  leaving  the  glycerin  free. 


—14— 

The  fats  occur  mixed  together  iu  the  bodj'.     Their  fusion 
points  diiJer.     Their  molecule  contains  much  more  C  and  H 
in  proportion  to  O  than  does  that  of  carbohydrates. 
CARBOHYDRATES.— Co/nposf(i  of  C,  H,  and  0. 

Dextrose  or  gi*ape  sugar  (C6H12O6);    capable  of  alcoholic 
fermentation;  of  lactic  acid  fermentation. 

Lactose  or  milk  sugar  (C12H22O11);   capable  of  lactic  acid 
fermentation. 

Inosit  (  CRHi20(i);  capable  of  lactic  acid  fermentation. 

Glycogen  ( CsHioOo ) ;  convertible  into  dextrose. 

Dextrin  ( CeHioOo ) ;  convertible  into  dextrose. 

SOME  OF  THE  SUBSTANCES  FORMED  IN  THE  BODY! 
FOR  THE  MOST  PART  '•  WASTE  "  PRODUCTS  OF  TIS- 
SUE CHANGE. 

XOX-XITROGEXOUS  METABOLITES. 

Lactic  acid  (CnHuOs). 

Oxalic  acid  (H2G2O+),  in  oxalate  of  lime. 

Succinic  acid  (HiCiH^Oi)- 

X^ITROGEX^OUS  METABOLITES. 
Urea  (NH2).C0;  and  its  oxalate  and  nitrate. 
Uric  acid  ( CsHiN^Os ) ;  and  salts. 
Kreatin  (C4H9N.O2). 
Kreatinin  (CiHrNaO). 
Sarkin  (C5H4N.O). 

(  ChHuG  ) 
Leucin   •<  )■  O. 

I    NH2    i 

Tyrosin  (CaHuNOs). 

Hippuric  acid  (C9H9NG3). 

Taurocholic  acid  ( G26H45NSO;). 

Glycocholic  acid  (GifiH^NGG). 

DEMONSTRATIONS. 

The  reactions  of  proteids  and  characteristics  of  their  groups. 
The  indiffusibility  of  albumin  and  dialysis  of  common  salt. 


—15— 

V,  EPITHELIUM,  CONNECTIVE  TISSUE.  BONE,  AND  PHYSIOLOGY  OF 
THE  SKELETON, 

EPITHELIUM. 

The  typical  aiiiinal  cell;  cell  ineinbrane;  protoplasm;  gran- 
ules; uucleuH  and  nucleoli;  fibrillar  net- work. 

Scaly  or  squamous  epithelium;  epidermis  and  buccal  mu- 
cous membrane. 

Columnar  epithelium;  intestine. 

Pavement  epithelium;  mesentery. 

Polyhedral  epithelium;  glands. 

Ciliated  epithelium;  trachea. 

Difference  between  "serous"  and  "mucous"  membranes. 

THE  CONNECTIVE  TISSUES. 

Function  and  distribution  in  the  body. 

White  fibrous  tissue ;  physical  characters ;  swelled  by  acids ; 
distribution. 

Yellow  elastic  tissue;  physical  characters;  unaffected  by 
acids ;  distribution. 

Cement  substance. 

Connective  tissue  corpuscles;  varieties  of  form  and  func- 
tion ;  distribution. 

Reteform  or  adenoid  tissue. 

Gelatinous  tissue;  vitreous  humor;  umbilical  cord. 

Areolar  tissue;  composition  and  distribution. 

The  development  and  condition  of  fat  in  the  body. 

THE  PERMANENT  SKELETON.— CARTILAGE. 

Hyaline  cartilage;  its  physical  characters;  the  perichon- 
drium; contains  no  blood  vessels;  histological  appearance; 
cells  and  matrix;  method  of  formation  of  matrix;  transition 
forms  between  round  cartilage  cells  and  branched  periosteal 
cells;  distribution  and  function. 

Fibro-cartilage;  physical  and  histological  characters;  action 
of  acids;  distribution  and  function. 


—16— 

Elastic-cartilage.     Parenchymatous  cartilage;  physical  and 

histological  characters;  unaffected  by  acids;  distribution  and 

functions. 

THE   BONY  SKELETON. 

The  skeleton  should  be  made  of  parts  which  are  strong, 
light,  inflexible  and  symmetrical. 

Bones  are  composed  of  a  mixture  of  organic  and  earthy 
matter. 

The  former  is  flexible,  the  latter  stiff  and  brittle;  the  origi- 
nal size  and  shape  of  the  bone  are  retained  when  either  is 
removed. 

Two-thirds  of  the  weight  of  dry  bone  is  mineral,  chiefly 
Cas  2  (P  O,). 

Mechanical  advantage  of  this  combination. 

THE  LONG  BONES. 

The  periosteum,  the  nutritive  membrane. 

The  expanded  articular  end  of  long  bones  allows  distribu- 
tion of  strain. 

The  advantage  gained  by  the  hollow  cylindrical  form  of 
the  bone. 

The  cancellated  extremities  and  the  red  and  white  marrow. 

Histological  structure  of  a  long  bone;  the  perfection  of 
adaptation  for  firmness,  lightness  and  elasticity. 

THE  SKULL. 

Advantage  of  its  curved  shape. 

The  two  bony  tables  with  diploe  between. 

The  outer  bony  plate  is  thicker,  tough  and  fibrous. 

The  inner  bony  plate  is  thinner,  dense  and  brittle. 

Use  of  deploe  in  deadening  jars. 

Use  of  the  sutures  in  limiting  the  extension  of  jars. 

THE  BACKBONE. 

The  separate  vertebrae  allow  the  bending  of  the  spine. 
The  intervertebral  pads  allow  bending  without  separation 
of  vertebrae,  and  deaden  jars. 


--17— 

The  curved  shape  of  the  spine  gives  it  a  wide  range  of 
elasticity. 

JOINTS. 

Ball  and  socket  joints. 

Hinge  joints. 

Pivot  joints. 

Gliding  joints. 

The  synovial  sac  and  its  infliience. 

The  capsular  ligament. 

Bones  are  held  together  by  atmospheric  pressure. 

THE  BONY  LEVERS. 
Lever  of  the  first  order;  nodding  motion 

of  the  head.         ..... 

Lever  of  the  second  order;  raising  the  body 
on  the  toes  by  the  calf  muscles. 

Lever  of  the  third  order;  raising  of  fore- 
arm by  the  biceps  muscle. 

DEMONSTRATIONS. 
Tendon. 

Ligamentum  nuchas. 

Mesentery. 

Costal  cartilage. 

Articular  cartilage. 

Intervertebral  cartilage. 

Elastic  cartilage. 

Decalcified  bone. 

Sections  of  long  bone  and  skull. 

The  skeleton. 


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—18— 

VI.    THE  CONTRACTILE  TISSUES. 

AMCEBOID  CELLS.     CILIATED  CELLS.     MUSCLES. 

Contractility  is  a  function  of  Protoplasm  irrespective  of 
any  special  form  in  which  this  matter  may  be  found. 

All  visible  movements  of  higher  animals  are  due  to  the 
contraction  oi  a  special  set  of  organs,  the  muscles,  which  are 
in  no- case  able  to  set  up  movements  spontaneously. 

The  amoeboid  cells  contract  throughout  their  body  sub- 
stance and  have  usually  the  power  of  locomotion. 

CILIATED  CELLS; 

Ciliated  cells  are  fixed  and  are  usually  columnar  in  shape. 

The  free  margin  of  the  cell  is  thick  and  firm,  and  has  pro- 
jecting from  it  ten  to  thirty  long  protoplasmic  lashes,  the 
cilia. 
.    The  movement  of  the  cilia  is  a  to  and  fro  whipping  motion. 

The  movement  is  two  or  three  times  quicker  in  one  direc- 
tion than  in  the  other. 

Foreign  bodies  resting  upon  the  cilia  are  urged  in  the 
direction  of  the  more  rapid  motion. 

The  function  of  cilia  in  the  trachea  and  bronchi:  they 
cause  expulsion  of  foreign  particles  and  aid  the  mixture  of 
gases. 

'  The  movement  is  automatic  and  co-ordinated.  The  move- 
inent  of  a  series  of  cilia  is  not  isochronous,  but  proceeds  in  a 
wave  form  along  the  row. 

The  impulse  to  the  movement  is  probably  conveyed  directly 
from  the  protoplasm  of  one  cell  to  that  of  the  next. 

The  energy  produced  by  each  cell  is  calculated  as  sufiicient 
to  raise  its  own  weight  each  minute  4^  metres. 

THE  MUSCLES. 

The  muscles  are  not  automatically  contractile. 
They  are  usually  red  in  color  from  contained  haemoglobin, 
but  the  color  is  not  essential. 

There  are  two  great  groups  which  are  distinguished  histo- 


-19- 

logically  atid  j)hysiologically:  (1)  Plain  or  unstriated  muscle; 
sometimes  called  visceral  or  organic  or  involuntary  muscle. 
(2)  Cross-striated  muscle;  sometimes  called  skeletal  or  vol- 
untary muscle. 

All  striated  muscles  contract  quickly  after  a  short  latent 
period. 

All  non-striated  muscles  contract  slowly  after  a  long  latent 
period. 

The  visceral  or  involuntary  muscles  of  some  animals  are 
striated. 

HISTOLOGY  or   NON-STRIATED  MUSOLE. 

The  llattened  lanceolate  cell;  the  rod-shaped  nucleus. 

The  method  of  aggregation  of  the  muscle  cells,  and  their 
distribution  in  the  body. 

THE  STEIATED  MUSCLE. 

The  manner  of  aggregation  of  muscle  and  other  tissues  as 
shown  in  the  cross  section  of  a  limb.  Each  muscle  is  made 
up  of  separate  bundles  of  fibres. 

The  fibres  may  be  oblique  or  parallel  to  the  long  axis  of 
the  muscle. 

The  length  of  the  muscle  fibre  in  man  varies  from  two  feet 
to  one  quarter  of  an  inch. 

The  union  of  muscle  with  tendon. 

HISTOLOGY  OF  STRIATED  MUSCLE. 

The  muscle  fibre;  the  sarcolemma;  the  nuclei;  the  cross 
markings. 

The  cross  marking  is  due  to  alternate  bright,  dark  and  dim 
bands. 

The  juncture  of  muscle  fibres  by  their  beveled  endings. 

Two  modes  of  ending  in  tendon. 

The  greater  part  of  the  living  muscle  fibre  is  semi-fluid  in 
consistency. 

PHYSIOLOGY  OF  STRIATED  MUSCLE. 

The  function  of  the  muscle  fibre  is  to  contract  or  to  draw 
its  two  ends  nearer  together. 


—20— 

Muscle  exists  in  the  body  in  two  natural  conditions,  in  art 
active  and  a  passive  state;  the  shape  and  elastic  properties  of 
the  muscle  are  different  in  the  two  conditions. 

The  shortening  of  the  muscle  is  active  and  due  to  distinct 
chemical  processes;  the  elongation  is  passive. 

The  shortening  is  caused  by  the  tranverse  swelling  of  the 
fibres. 

The  muscle  does  not  preceptibly  alter  in  volume  in  contrac- 
tion. 

The  molecular  cause  of  contraction  is  probably  the  absorp- 
tion of  the  more  fluid  parts  of  the  muscle  fibres  within  defi- 
nite layers  of  more  solid  particles. 

Whatever  excites  a  muscle  to  contract  is  called  a  stimulus. 

The  contraction  begins  at  the  point  stimulated,  and  moves 
along  the  fibre  in  the  form  of  a  wave,  which  travels  in  the 
frog's  muscle  with  a  velocity  of  about  three  metres  per  sec- 
ond.    The  wave  moves  slower  the  lower  the  temperature. 

THE  PHYSICAL  PROPERTIES  OF  MUSCLE. 

Compare  the  curve  of  elasticity  of  muscle  with  that  of  steel. 

Compare  the  curves  of  elasticity  of  resting  and  active  mus- 
cle. 

The  elasticity  of  resting  muscle  is  perfect  within  narrow 
limits. 

When  a  muscle  contracts,  its  elasticity  decreases  and  its 
extensibility  increases. 

The  resting  muscles  in  the  body  are  always  slightly 
stretched  between  their  attachments.  Proof  of  this  and  sig- 
nificance for  the  welfare  of  the  body. 

The  protective  use  to  the  body  of  the  increased  extensibil- 
ity of  contracted  muscle. 

The  elasticity  of  the  muscle  enables  it  to  store  up  its  energy 
of  contraction. 

The  lifting  power  of  the  muscle  diminishes  with  contrac- 
tion. 

Show  how  in  the  movements  of  the  bony  levers  the  con- 


-21— 

tractile  energy  of  the  muscle  is  economized  according  to  the 
preceding  principle. 

The  mnscle  ])ossesses  the  distinct  properties  of  coniractilUy, 
conductivity  and  irritahility. 

The  peculiar  nature  of  physiological  conductivity. 

Irritability  is  the  capability  possessed  by  some  tissues  of 
being  stirred  up  to  functional  activity  by  a  stimulus. 

Its  peculiarity  is  the  disproportion  between  the  amount  of 
energy  represented  in  the  stimulus  and  in  the  effect  produced. 

Irritability  is  decreased  by  low  temperature,  by  fatigue,  by 
various  drugs. 

,     The  old  view  that  coniraction  of  jnuscle  was  due  to  swelling 
of  its  substance  by  the  in-fiow  of  "animal  spirits." 

Proofs  of  the  independent  irritability  of  muscle;  contrac- 
tion of  embryonic  muscles  before  the  establishment  of  nervous 
connections;  the  "  idio-muscular  "  contraction;  the  nerve  free 
ends  of  the  sartorius;  the  manner  of  action  of  curare. 

The  various  kinds  of  stimuli  capable  of  exciting  muscle; 
nervous;  mechanical;  thermal;  chemical;  electrical. 

The  character  of  a  muscular  contraction  caused  by  the 
application  of  a  galvanic  current. 

The  contraction  caused  by  a  single  inductive  shock. 

The  general  law  for  the  stimulation  of  irritable  tissues:  It 
is  only  the  cJiange  of  intensity  of  a  stimulus  that  excites  an 
irritable  organ. 

The  most  favorable  rate  of  change  of  intensity  of  the  stim- 
ulus differs  for  different  kinds  of  tissues;  the  intensity  should 
vary  most  rapidly  for  nerve,  less  so  for  striped  muscle,  and 
still  more  slowly  for  unstriped  muscle. 

The  muscle  answers  a  single  stimulation  by  a  single  twitch 
or  contraction. 

The  contraction  is  prolonged  by  cold,  by  fatigue,  by  various 
drugs. 


—22— 

The  curve  o£  a  single  muscular  contraction;  the  latent 
period  of  stimulation;  the  phases  of  the  contraction  curve;  the 
"contractur." 

The  latent  period  of  stimulation  is  the  interval  elapsing 
between  the  application  of  a  stimulus  and  the  beginning  of 
contraction.  Its  average  duration  in  the  frog's  muscle  is  .01 
second.  During  the  latent  period  the  muscle  molecules  are 
undergoing  chemical,  electrical,  thermal  and  mechanical 
changes.  The  period  is  lengthened  by  cold,  by  fatigue,  by 
increased  load. 

The  "contractur"  is  due  to  the  "elastic  after  action"  of  the 
muscle  substance,  not  to  vital  changes.  Influence  of  fatigue 
and  of  load  upon  the  contractur. 

Maximal  and  sub-maximal  single  contractions;  with  a  cer- 
tain strength  of  stimulus  the  muscle  gives  a  barely  visible 
contraction;  with  increase  of  stimulus  the  height  of  contrac- 
tion increases  to  a  certain  extent,  and  then  no  stronger  stim- 
ulus causes  a  greater  single  contraction. 

The  fatigue  curve  of  muscle  excited  to  single  contractions 
repeated  at  a  definite  rate  is  a  straight  line.  The  line  falls 
more  rapidly  with  a  shorter  interval  between  the  stimuli.  The 
effect  of  rest  is  to  increase  the  height  of  the  succeeding  con- 
traction. 

The  waste  products  of  contraction  diminish  the  irritability 
and  contractility  of  the  muscle.  A  blood  free  muscle  exhausted 
by  stimulation  may  be  made  to  contract  again  after  washing 
out  with  dilute  salt  solution. 

The  work  done  by  a  contracting  muscle  is  measured  by  the 
load  X  height  of  lift.  The  work  done  increases  with  the  load 
to  a  certain  extent  and  then  diminishes  as  the  load  becomes 
greater. 

The  lift  power  of  a  muscle  increases  with  its  thickness,  or 
the  number  of  fibres  side  by  side.     The  extent  of  the  short- 
ening increases  with  the  length  of  the  fibres. 
PHYSIOLOGICAL  TETANUS. 

When  one  contraction  succeeds  another  in  a  muscle  before 


—28— 

the  first  is  finished,  the  result  is  a  longer  and  more  extensive 
contraction  or  fcfaaiis.  The  tetanus  is  smooth  when  each 
contraction  ])egins  during  the  ascending  phase  of  the  preced- 
ing one.  The  tetanus  is  vibratory  when  the  muscle  has  time 
to  relax  from  one  contraction  before  another  engages  it. 

Proof  of  the  formation  (^f  tetanus  by  the  summation  of 
single  contractions. 

A  tetanus  may  he  sub-maximal  or  maximal  in  extent. 

A  muscle  may  be  shortened  by  tetanus  to  one-third  its 
original  length. 

In  tetanus  the  dni-ation,  the  (DiipJifiide,  and  the  power  of 
the  contraction  may  be  made  greater  than  by  the  use  of  a 
single  stimulus. 

The  natural  contractions  of  the  living  body  are  sub-maxi- 
mal and  tetanic  in  character. 

Pi  oofs  of  the  foregoing  statement:  comparison  of  the 
power  of  voluntary  and  artificially  excited  contractions.  The 
duration  of  the  shortest  voluntary  contraction  compared  with 
that  excited  by  a  single  artificial  stimulation.  The  muscle 
note  and  its  pitch. 

Voluntary  contractions  are  probably  due  not  to  the  simul- 
taneous, but  to  the  successive  stimulation  of  the  different  fibres 
of  a  muscle. 

Free  circulation  of  blood  in  the  muscle  is  necessary  to  vol- 
untary contraction. 

THE  ELECTRICAL  PHENOMENA  OF  ACTIVE  MUSCLE. 

When  a  muscle  is  stimulated,  the  part  excited  becomes 
electro-negative  to  the  resting  parts. 

The  electric  change  is  due  to  the  chemical  changes  of  the 
active  molecules. 

The  chemical  change  set  up  in  the  muscle  by  stimulation 
is  conducted  along  the  fibres,  and  the  electro-negative  con- 
dition accompanies  it. 

The  rate  of  this  progression  in  the  frog's  muscle  is  about 
three  metres  per  second.  It  has  already  finished  its  course 
during  the  latent  period  of  stimulation. 


—24— 

If  an  electric  conductor  be  made  to  connect  tlie  excited 
electro-negative  part  of  the  muscle  with,  its  resting  electro- 
positive part,  a  current  of  electricity  will  ilow  through  the 
conductor.  This  current  is  called  the  "action  current"  of 
the  muscle. 

The  physiological  action  current  is  not  to  be  confused  with 
the  electrical  current  which  is  used  as  a  stimulus. 

Experiment  of  the  "rheoscopic  frog."  The  secondary  mus- 
cle is  thrown  into  tetanus  when  the  primary  muscle  is  tetan- 
ied,  thus  proving  the  interrupted  nature  of  the  electric  changes 
in  the  latter. 

When  the  vital  continuity  of  the  nerve  supplying  the  first 
muscle  is  broken  by  tying  a  string  around  it,  the  tetanus  fails 
in  both  muscles. 

An  action  current  is  set  up  in  a  muscle  by  any  stimulus, 
electrical  or  otherwise. 

The  secondary  contraction  of  a  frog's  nerve-muscle  prepar- 
ation caused  by  the  beat  of  the  mammalian  heart. 

COMPARISON  OF  THE  PHYSICAL  AND  CHEMICAL  CHAR- 
ACTERS OF  LIVING  AND  DEAD  MUSCLES. 

Living  resting  muscle  is  soft,  glistening,  elastic,  semi-trans- 
parent and  alkaline  or  amphichroic  in  reaction. 

Living  working  muscle  is  less  elastic,  but  more  extensible 
and  becomes  acid  in  reaction. 

Dead  muscle  is  dull,  opaque,  inelastic  and  is  acid  in  re- 
action. 

A  dying  muscle  loses  gradually  its  irritability,  antl  then 
goes  rather  suddenly  into  rigor  mortis.  Rigor  is  attended  by 
a  considerable  production  of  sarcolactic  and  carbonic  acids, 
by  a  rise  of  temperature,  and  by  a  shortening  of  the  muscle. 
Rigor  passes  off  as  decomposition  sets  in. 

THE  CHEMICAL  CHANGES  OF  WORKING  MUSCLE. 
The  excised  muscle  gives  off   no  oxygen  under  the   air 
pump,  but  when  made  to  contract  it  develops  sarcolactic  and 
carbonic  acids  in  an  oxygen  free  atmosphere. 


—  25  — 

The  living  muscle  in  the  body  consumes  more  oxygen,  and 
produces  more  carbonic  acid  in  the  active  than  in  tiie  resting 
condition. 

The  weight  of  muscle  substance  soluble  in  water  decreases, 
Avliile  that  soluble  in  alcohol  increases  in  the  active  as  com- 
pared with  the  resting  condition. 

The  amount  of  acid  produced  by  tetanising  an  excised 
muscle  is  substracted  from  the  amount  finally  produced  by 
the  death  of  the  muscle. 

The  living  muscle  molecule  probably  consists  of  an  essen- 
tial nitrogenous  part  capable  of  building  on  to  itself  certain 
carbon  compounds  by  whose  oxidation  the  energy  of  contrac- 
tion is  produced. 

Every  contraction  is  attended  by  an  evolution  of  heat. 

Comparison  of  the  muscle  with  the  steam-engine. 

THE  CHEMISTRY  OF  LIVIXG  MUSCLE. 

The  contents  of  the  living  muscle  fibre  are  chiefly  semi- 
fluid in  consistency.     This  matter  is  the  muscle  plasma. 

The  artificial  preparation  of  muscle  plasma. 

The  clotting  of  muscle  plasma  and  its  separation  into  clot 
and  serum. 

The  muscle  clot  is  myosin j  its  formation  in  dead  muscle 
causes  ligor  mortis. 

The  clot  of  myosin  is  granular;  its  formation  is  accompa- 
nied by  the  development  of  acid. 

THE  CHEMISTRY  OF  DEAD  MUSCLE. 

The  dead  muscle  contains  seventy-five  per  cent,  water.  Its 
dry  substance  contains: — 

Proteids;  myosin;  serum-albumin. 

Extractives;  kreatin;  sarcolactic  acid;  xanthin;  hyjDoxan- 
thin;  uric  acid;  inosit  (in  the  heart);  iuosinic  acid;  sugar. 

No  urea. 

Fats  in  quantity. 

In  living  muscle  there  is  glycogen  which  is  changed  to 
sugar  on  death.     The  nitrogenous  extractives  are  products  of 


—  26  — 

the  chemical  changes  of  the  muscle  substance.     Myosin  does 
not  exist  in  living  muscle. 

THE  PHYSIOLOGY  OF  UNSTRIATED  MUSCLE. 

Unstriated  muscle  is  not  found  unmixed  with  other  tissues 
of  the  body. 

Organs  containing  unstriated  muscle  have  to  some  extent 
power  of  automatic  contraction,  which  may  be  due  to  con- 
tained nervous  elements. 

The  contraction  progresses  slowly  in  a  wave  form  from  the 
spot  stimulated,  and  is  preceded  by  a  long  latent  period. 

In  striated  muscle  the  contraction  wave  passes  only  length- 
wise throughout  the  fibre;  in  unstriated  muscle  the  wave  may 
pass  both  in  the  direction  of  the  length  and  the  breadth  of 
the  cell. 

The  impulse  to  contraction  may  probably  be  communicated 
directly  by  one  muscle  cell  to  another  without  the  interven- 
tion of  nerves. 

Unstriated  muscle  is  more  readily  stimulated  by  the  make 
and  break  of  a  galvanic  current  than  by  induction  currents. 

Consider  the  action  of  unstriated  muscle  as  seen  in  the 
peristaltic  action  of  the  intestine  and  ureter  and  in  the  con- 
traction of  the  urinary  bladder. 

DEMONSTRATIONS. 

The  motor  power  of  cilia. 

Comparison  of  the  contractions  of  striated  and  unstriated 
muscles  in  a  rabbit. 

The  contraction  of  muscle  on  mercury. 

The  dimiliution  of  lifting  power  with  the  shortening. 

The  single  muscular  contraction  and  its  curve. 

Physiological  tetanus  and  its  curve. 

The  analysis  of  tetanus. 

Maximal  and  sub-maximal  contractions. 

Contraction  with  the  constant  current. 

The  action  of  curare. 


—27— 

The  rh(?oscopic  hog;  secondary  tetanus. 
Secondary  contraction  of  frog's  muscle  from  the  beat  of 
the  mammalian  heart. 

Formation  of  acid  with  the  death  of  the  muscle. 

VII.    NERVOUS  TISSUES. 

The  nervous  tissues  consist  of  the  nerves  and  of  the  per- 
ipheral and  central  irritable  non-contractile  organs  in  which 
they  end. 

THE  MINUTE  STRUCTURE  OF  NERVES. 

Nerve  fibres  are  bound  together  in  bundles,  the  funiculi. 

Each  funiculus  is  inclosed  in  several  sheets  of  membrane, 
the  neurilemma.  Each  nerve  is  composed  of  many  funiculi 
inclosed  in  a  common  sheath. 

The  lymph  channels  of  nerves. 

Nerve  fibres  fall  into  two  groups :  ( 1 )  MeduUated  or  white 
nerve  fibres.  (2)  Non-medullated,  gray  or  sympathetic 
nerve  fibres. 

Histology  of  the  medullated  fibre;  the  primitive  sheath; 
the  medullary  sheath  or  white  substance;  the  axis  cylinder; 
the  neuro-keratin  frame- work;  the  nodes  of  Kanvier;  the 
cement  substance;  the  nuclei. 

Significance  of  the  nodes  in  the  nutrition  of  the  nerve. 

The  medullary  sheath  is  chiefly  fat,  and  is  not  differentiated 
in  perfectly  fresh  nerve. 

The  axis  cylinder  is  protoplasmic  and  is  the  conductor  of 
the  nervous  impulse. 

Nerves  lose  their  medullary  sheath  before  reaching  their 
peripheral  and  central  terminations. 

The  ending  of  nerves  in  voluntary  muscle;  ending  in 
involuntary  muscle. 

Histology  of  gray  nerve  fibre;  absence  of  medullary  sheath; 
nuclei  found  in  the  substance  of  the  fibre. 

The  physiology  of  gray  nerve  fibre. 


—28-- 

In  general,  the  gray  nerve  fibres  arise  from  the  sympathetic 
system  and  are  distributed  to  organs  whose  function  does  not 
involve  consciousness. 

CLASSIFICATION  OF  NERVES   ACCORDING  TO  THEIR 
FUNCTIONS.     (MARTIN.) 

f  Sensory. 
I   Reflex. 
Afferent.  ~{   Excito-motor. 
Vaso-motor. 
l^  Inhibitory  ? 
Peripheral  Nerves.  ^ 

f  Motor. 
I   Vaso-motor. 
Efferent.  -\   Secretory. 
I   Trophic  ? 
i^  Inhibitory. 

(  Exciting. 
Intercentral  Nerves.  <  Inhibitory. 

(  Commissural. 

PHYSIOLOGY  OF  NERVES. 

The  nerve  has  not  automaticity,  but  possesses  to  a  high 
degree  in'ifabilify  and  conduct iv if  ij. 

The  nerve  is  excited  only  by  the  change  of  intensity  of  a 
stimulus. 

The  nerve  is  excited  by  a  much  weaker  induction  shock 
than  is  the  muscle. 

Various  nerve  stimuli;  mechanical;  chemical;  electrical. 

The  change  started  by  an  artificial  stimulation  travels  as  a 
nervous  impulse  along  the  nerve  in  both  directions. 

As  in  the  muscle,  the  excited  parts  of  the  nerve  are  electro- 
negative to  the  resting  parts.  Tlie  action  current  and  the 
change  causing  it,  travel  along  the  nerve  of  the  frog  at  the 
rate  of  about  twenty-eight  metres  per  second,  and  of  man 
thirty-three  metres  per  second. 

The  irritability  of  the  nerve  and  its  rate  of  conduction  in- 
crease with  the  temperature. 


—29— 

The  energy  of  the  nervous  impulse  is  small  in  amount.  Nd 
heat  can  be  shown  to  be  evolved,  and  no  chemical  change  to 
take  place  as  a  result  of  nervous  activity. 

All  the  phenomena  of  muscular  contraction  obtained  by  the 
direct  stimulation  of  the  muscle  substance  may  be  obtained 
by  its  indirect  stimulation  through  the  nerve. 

The  degeneration  and  regeneration  of  cut  nerves. 

ELECTROTONUS. 

When  a  motor  nerve  is  subjected  to  the  passage  of  a  con- 
stant current  of  electricity  the  muscle  supplied  by  it  contracts 
only  at  the  make  and  break  of  the  current  in  the  nerve,  and 
remains  at  rest  during  the  passage  of  the  current. 

The  passage  of  a  galvanic  current  modifies  the  irritability 
and  conductivity  of  the  nerve. 

The  irritability  and  conductivity  of  the  nerve  are  diminished 
in  the  neighborhood  of  the  anode,  and  ina-eased  in  that  of  the 
kaihodc  of  the  constant  current. 

In  the  region  of  diminished  irritability  the  nerve  is  said  to 
be  in  the  state  of  anelech'ofoniis.  In  the  area  of  exalted  irrit- 
ability the  nerve  is  said  to  be  in  kathelectrotonus. 

The  electrotonic  conditions  are  more  marked  the  stronger 
the  galvanic  current  used. 

Proofs  of  the  electrotonic  modifications  of  irritability  as  ex- 
hibited on  the  excised  nerve-muscle  of  the  frog  and  on  the 
human  arm. 

Application  of  the  principles  of  electrotonus  to  electro- 
therapeutics. 

The  "law  of  contraction"  and  its  meaning. 

DEMONSTRATIONS. 

The  indirect  stimulation  of  muscle  through  the  nerve. 

Maximal,  sub-maximal  contractions  and  tetanus  indirectly 
obtained. 

Proof  of  the  greater  irritability  of  nerve-muscle  than  of 
curarised  muscle  toward  induction  shocks. 


—30- 


Various  nerve   stimuli;    chemical;   mechanical;    electrical 
Contraction  with  the  use  of  the  galvanic  current. 
The  electrotonic  modification  of  irritability  of  nerve. 
The  law  of  contraction. 


VIII.    REFLEX  ACTION  AND  THE  MECHANISMS  INVOLVED  IN  IT. 

The  origin  of  nerves  from  nerve  cells. 

Various  forms  of  ganglion  cells.  Nerve  cells  in  sporadic 
ganglia;  in  the  spinal  cord;  in  the  cerebellum ;  in  the  cerebrum. 

In  the  living  body  every  contraction  of  the  skeletal  muscles 
is  due  to  stimuli  proceeding  from  nerve  cells. 

NATURE  OF  THE  CONTRACTIONS  PRODUCED  BY  THE 
DIRECT  STIMULATION  OF  THE  NERVE  CELLS. 

Make  one  cut  across  a  motor  nerve  and  the  muscle  supplied 
by  it  contracts  but  once. 

Cut  across  the  spinal  cord  of  a  frog  and  its  muscles  are 
thrown  into  ieidiius. 

The  tetanus  involves  only  the  flexor  muscles  if  the  section 
be  made  across  the  anterior  part  of  the  cord.  Only  the  exten- 
sor muscles  are  contracted  if  the  section  severs  the  posterior 
part  of  the  cord. 

The  experiment  indicates  that  a  nerve  cell  when  artificially 
excited  may  continue  to  send  out  discharges  after  cessation  of 
the  stimulation.  Also  that  there  is  localization  of  motor  func- 
tion in  the  spinal  cord. 

REFLEX  ACTION. 

Nerve  cells  communicate  with  the  exterior,  by  means  of 
afferent  nerve  fibres  which  terminate  in  modified  end  organs. 

External  phenomena  excite  afferent  nerves  through  the 
medium  of  sense  oirjans  in  which  those  nerves  terminate 
peripherally. 

The  nervous  organs  in  which  nerves  terminate  are  excited 
only  by  a  change  in  the  intensity  of  a  stimulus. 


— ;n— 

Examples  of  sense  organs ;  the  retina ;  the  organ  of  Corti ; 
tactile  corpnscles. 

The  reliex  action  ()l)taine(l  l)y  dipping  the  toe  of  a  headless 
frog  into  dilute  acid. 

Characters  of  the  retlex.  The  latent  period  or  rcfic.r  fiine. 
The  apparently  purposeful  character  of  the  reflex  in  remov- 
ing irritating  sul)stances. 

Purposeful  character  of  a  reflex  as  shown  in  sneezing  and 
coughing. 

The  kind  of  reflex  action  illustrated  in  the  secretion  of 
saliva, 

A  single  stimulus  with  difficulty  provokes  a  reflex,  but  a 
succession  of  stimuli  readily  does  so.  Summation  of  stimuli 
in  the  spinal  cord. 

Increase  of  strength  of  stimulation  or  increase  of  its  rate 
shortens  reflex  time. 

The  reflex  time  is  the  period  occupied  chiefly  by  processes 
in  the  nerve  cells. 

The  unco-ordinate  nature  of  reflexes  obtained  by  direct 
stimulation  of  the  afferent  nerve. 

The  value  of  tlie  peripheral  nervous  organ  in  reflex  action. 
Each  sense  organ  is  differentiated  to  be  specially  irritable 
toward  one  certain  form  of  energy. 

Radiation  of  nervous  impulses  in  the  cord. 

The  purposeful  character  of  reflex  actions  explained  not  l^y 
consciousness  of  the  cord  but  by  the  choice  of  paihs  of  least 
resisiance  which  determine  the  direction  taken  in  the  cord  by 
impulses  arising  from  any  quarter. 

Any  segment  of  the  spinal  cord  may  act  as  a  reflex  centre. 

The  typical  mechanisms  employed  in  a  normal  reflex  action 
are:  A  peripheral  organ  for  the  reception  of  the  stimulus;  an 
afferent  nerve  fibre,  a  single  nerve  cell  or  a  sensory  and  a 
motor  cell,  an  efferent  nerve  fibre,  a  peripheral  motor  or 
glandular  organ. 

The  essential  characters  of  a  reflex  action  are:  (1)  Its 
unconsciousness;  (2)  the  want  of  likeness  between  the  effects 


-32— 

produced  and  the  nature  and  method  of  the  stimulation 
employed;  (3)  the  usually  co-ordinated  nature  of  the  action. 

The  most  rapid  action  of  which  the  central  nervous  system 
is  capable  is  manifested  in  reflexes. 

Eeflex  action,  as  such,  are  adapted  to  the  protection  of  the 
body  against  accidents,  and  are  also  continually  employed  in 
the  organic  processes  of  the  body. 

Modification  of  the  conductivity  of  the  spinal  cord  in 
strychnia  poisoning. 

INHIBITION. 

The  activity  of  a  nervous  centre  is  the  resultant  of  two 
forces,  one  exciting  to  discharge  and  the  other  resisting  dis- 
charge. Forces  resisting  or  depressing  activity  are  termed 
Inhibitory. 

The  resistance  to  the  action  of  any  nerve  cell  seems  to  be 
increased  by  its  association  with  the  nerve  cells  in  physiolo- 
gical connection  with  it. 

Inhibitory  influences  may  reach  an  active  nerve  cell  from 
any  quarter,  as  along  any  afferent  nerve. 

Consider  the  inhibition  of  a  reflex  action  through  the  strong 
stimulation  of  afferent  nerve. 

There  appear  to  be  in  the  brain  special  inhibitory  centres 
whose  business  it  is  to  send  out  impulses  to  retard  or  depress 
the  activities  of  the  body. 

Consider  the  inhibitory  effect  upon  reflex  action  in  the  frog 
of  stimulation  of  the  optic  lobes.  The  inhibition  of  the  beat 
of  the  heart. 

The  general  function  of  inhibitory  centres  is  to  control  and 
make  more  effective  the  activities  of  motor  centres. 

Reflex  time  is  the  period  occupied  by  a  stimulus  in  over- 
coming the  resistance  to  discharge  offered  by  the  nerve  cell. 

The  physiological  relation  of  reflex  and  voluntary  actions. 

Cerebral  time. 


—33— 

The  tendon  reflex. 

Muscular  tone. 

There  is  no  proof  th;it  the  sporadic  ganglia  of  the  body  can 
serve  as  reflex  centres. 

The  physiological  afferent  and  efferent  nerve  flbres  are 
mixed  together  in  the  nerve  trunks,  but  l)efore  reaching  the 
spinal  cord  the  sensory  and  motor  fibres  separate,  the  former 
joining  the  cord  by  the  posterior  spinal  roots,  and  the  latter 
by  the  anterior  roots. 

DEMONSTRATIONS. 

Tetanus  following  section  of  the  spinal  cord  in  the  frog. 

Reflex  actions  from  headless  frogs  brought  about  by  me- 
chanical, electrical  and  chemical  stimulatisn.  Influence  of  the 
strength  of  the  stimulus.  Influence  of  the  rate  of  stimula- 
tion. 

Reflex  from  stimulation  of  an  afferent  nerve. 

The  summation  of  stimuli  in  the  nervous  centre. 

The  purposeful  and  co-ordinated  character  of  the  reflex 
shown  in  the  removal  of  acid  paper. 

Inhibition  of  reflex  by  stimulation  of  an  afferent  nerve. 

Influence  ujjon  reflex  time  of  stimulation  of  the  optic  lobes 
in  the  frog. 

Effect  of  strychnia  upon  the  frog. 

Demonstration  upon  the  frog  of  the  functions  of  the  spinal 
nerve  roots. 


IX.    THE  CIRCULATION  UP  THE  BLUUU,  AND  THE  ORGANS  OF 

CIRCULATION, 

THE  ANATOMY   AND   HISTOLOGY   OF  THE  MAMMA- 
LIAN HEART. 

The  pericardium;  its  shape,  dimensions,  and  manner  of 
attachment  to  the  heart  and  chest  wall. 

The  pericardial  fluid. 

The  division  of  the  heart  cavity  into  four  distinct  chambers, 
those  of  the  two  auricles  and  the  two  ventricles. 

The  marked  diff^erence  in  thickness  between  the  walls  of 
the  auricles  and  ventricles.  The  difference  between  the  walls 
of  the  right  and  left  ventricle. 

An  inner  layer  of  muscle  is  peculiar  to  each  auricle,  and  an 
outer  layer  is  common  to  both. 

The  spiral  arrangement  of  the  ventricular  muscle  fibres. 

The  comparative  volume  of  the  auricle  when  collapsed  and 
when  distended.     The  auricular  appendage. 

Compare  the  relative  size  of  the  four  chambers  of  the 
empty  heart. 

Notice  the  size,  shape,  and  manner  of  attachment  of  the 
mitral  and  tricuspid  valves.  The  muscle  fibres  upon  the 
upper  surface  of  the  valves.  The  papillary  muscles  and  the 
cJiordce  fendinece. 

The  Goliunnce  carnece. 

Notice  the  form  and  structure  of  the  vessels  springing 
from  the  heart. 

Notice  the  shape,  structure,  and  manner  of  attachment  of 
the  semiluucir  valves. 

Notice  the  shape  of  the  aorta  at  its  base,  and  the  postion  of 
the  openings  of  the  two  coronary  arteries. 


-36— 

Observe  the  fibrous  rings  surrounding  the  auriculo-ventri- 
cular  and  arterial  orifices. 

Notice  the  muscle  fibres  continuing  from  the  heart  upon 
the  surface  of  its  great  veins. 

The  endocardium. 

The  histological  characters  of  the  heart  muscle.  The  mus- 
cle is  made  up  of  striated,  nucleated  cells  not  enclosed  in 
sarcolemma. 

The  intrinsic  ganglia  of  the  heart. 

The  extra-cardiac  nerves : — ( 1 )  Fibres  from  the  vagus  nerve, 
including  physiological  efferent  cardio-inhibitory  and  physio- 
logical afferent  "depressor"  fibres.  (2)  Fibres  from  the 
spinal  cord  by  way  of  sympathetic  ganglia,  including  physio- 
logical efferent  "accelerator"  fibres. 

THE  STRUCTURE  OF  THE  BLOOD-VESSELS. 

Tunica  adventifia  of  the  arteries. 

The  thick  arterial  wall  and  open  lumen  of  the  empty  vessel. 

The  thin  walled  veins,  collapsing  when  empty. 

Minute  structure  of  a  small  artery  : — The  lining  epithelium. 
The  thickness  of  the  wall  composed  of  three  distinct  coats  : 
( 1 )  a  narrow  internal  coat  composed  chiefly  of  white  fibrous 
connective  tissue;  '(2)  a  thicker  middle  coat  of  circularly 
arranged  unstriped  muscle;  (3)  an  outer  less  firm  coat  com- 
posed of  mixed  yellow  elastic  and  white  fibrous  tissue. 

In  the  larger  arteries  the  constituents  of  the  three  coats 
intermingle,  while  in  the  arterioles  the  coats  are  sharply 
defined  one  from  the  other. 

The  muscular  element  becomes  proportionally  more  prom- 
inent as  we  proceed  from  the  larger  to  the  smaller  arteries. 

The  capillaries,  composed  entirely  of  the  vascular  endothe- 
lium cells  joined  edge  to  edge. 

The  structure  of  the  veins  corresponds  in  general  with  that 
of  the  arteries,  except  that  the  layer  of  muscle  is  not  so  well 
defined  nor  relatively  so  thick. 

The  valves  in  the  veins. 


-37- 

Compare  the  elasticity  of  the  artery  with  that  of  the  vein. 

The  artery  is  very  elastic,  its  walls  thick  and  strong.  Curve 
of  elasticity  of  the  arterial  wall.  The  vein  is  more  extensible 
than  the  artery,  and  more  easily  ruptured  when  fully  dis- 
tended. 

THE  PHYSIOLOGY  'OF  THE  HEART, 
THE  AURICULO- VENTRICULAR  VALVES. 

Notice  that  the  surface  of  the  valves  is  considerably  greater 
than  is  necessary  to  separate  completely  the  cavity  of  the 
auricle  from  that  of  the  ventricle  on  each  side  of  the  heart 

Notice  that  the  chordce  fendmece  are  attached  externally  not 
directly  to  the  heart  wall,  but  through  the  medium  of  the 
papillary  muscles.  The  function  of  these  muscles  in  keeping 
their  tendons  tense  as  the  heart  cavity  becomes  smaller  in 
contraction. 

The  inner  ends  of  chordce  springing  from  each  papillary 
muscle  are  attached  to  the  edges  not  of  a  single  valve  but  to 
those  of  two  adjacent  ones. 

The  auriculo-ventricular  valves  are  attached  at  their  outer 
edges  to  fibrous  rings  in  the  heart-wall. 

The  use  of  the  muscle  fibres  upon  the  upper  surface  of 
each  valve. 

The  floating  upward  of  the  auriculo-ventricular  valves  dur- 
ing the  pause  of  the  ventricle. 

The  function  of  the  auricle  in  completely  closing  by  its 
contraction  the  auriculo-ventricular  valves. 

The  manner  of  action  of  the  semilunar  valves, 

THE  FUNCTION  AND  COMPARATIVE  PHYSIOLOGY  OF 
THE  HEART. 

The  heart  acts  simply  as  a  pump  whose  valves  enable  it  to 
send  fluid  around  a  continuous  circuit. 

The  respective  functions  of  auricles  and  ventricles. 

Diagrams  illustrating  the  action  of  simple  and  complex 
pumps. 

5 


The  object  of  the  circulation  is  to  bring  new  material  to  the 
tissues  and  remove  waste  matters  from  them. 

The  mammalian  heart  is  a  double  pump;  one-half  of  which 
forces  out  venous  blood  and  the  other  half  arterial  blood. 
The  use  to  the  animal  of  this  complex  form  of  the  mammalian 
heart. 

Demonstration  of  the  movement  of  fluid  in  the  sheep's 
heart. 

The  co-ordination  throughout  the  animal  kingdom  of  the 
anatomical  structure  of  the  heart  with  the  physiological  needs 
of  the  organism. — The  contractile  circulatory  apparatus  of 
the  amoeba;  of  a  ivormj  of  a  snail;  of  a,  frog. 

THE  PHENOMENA  INVOLVED  IN  THE  CARDIAC  CYCLE. 

The  beat  of  the  excised  heart  of  the  frog.  The  active  sys- 
fole  and  the  passive  diastole.  The  rounder  base  and  shorter 
long  axis  of  the  heart  in  systole. 

The  position  of  the  mammalian  heart  in  the  living  body; 
the  change  of  position  on  opening  the  chest  wall. 

The  movements  of  the  living  heart  within  the  chest: — The 
slight  rotation  round  the  long  axis.  The  marked  movement 
of  base  toward  the  apex,  and  its  cause.  Effect  upon  the  posi- 
tion of  the  heart  and  on  the  movement  of  its  base,  of  bleed- 
ing.    The  absence  of  locomotion  in  the  apex. 

In  the  erect  position  of  the  body  the  apex  of  the  heart 
probably  persistently  touches  the  chest  wall,  and  the  cardiac 
impulse  is  due  to  the  hardening  of  the  ventricle  in  systole. 

The  phases  of  the  cardiac  cycle : — The  duration  of  the  auri- 
cular systole  and  the  condition  of  the  rest  of  the  heart  dur- 
ing it.  The  duration  of  the  ventricular  systole  and  the  con- 
dition of  the  rest  of  the  heart  during  it.  The  duration  of 
common  diastole  of  the  heart.  The  length  of  the  whole  car- 
diac cycle. 

The  nature  and  time  relations  of  the  changes  going  on 
within  the  various  chambers  of  the  heart  throughout  the  car- 
diac cycle.     The  experiments  of  Chauveau  and  Marey. 


— 3t)— 

The  cardiac*  systole  begins  in  the  great  veins. 

The  quick  peristaltic  contraction  of  the  auricles. 

The  long  persistence  of  the  phase  of  extreme  contraction 
in  the  ventricles. 

The  ventricles  probably  empty  themselves  completely  at 
each  systole.     The  auricles  never  do. 

THE  WORK  DONE  BY  THE  HEART. 

Factors  which  determine  the  amount  of  work  done  by  the 
heart: — (1)  The  amount  of  blood  pumped  out  at  each  beat; 
(2)  the  resistance  to  be  overcome;  (3)  the  frequency  of  the 
beats. 

Calculation  of  the  amount  of  work  done  by  the  human  heart 
in  24  hours. 

The  work  power  of  the  heart  is  alone  quite  sufficient  to 
cause  the  blood  to  circulate  through  the  whole  body. 

THE  SECONDARY  MECHANICAL  AIDS  TO  THE  WORK  OF 
THE  HEART. 

The  assistance  given  to  the  filling  of  the  auricles  by  the 
movements  of  inspiration. 

The  suction  of  blood  into  the  auricles  due  to  the  movement 
of  the  base  of  the  ventricle  when  the  latter  contracts. 

The  help  offered  by  the  coronary  circulation  to  the  filling 
of  the  ventricles. 

The  help  offered  by  the  elasticity  of  the  ventricular  wall  to 
the  filling  of  the  ventricle. 

The  circulatory  variations  in  organs  outside  the  heart  as 
shown  by  the  plethysmograph. 

The  aid  rendered  to  the  filling  of  the  ventricles  by  the  slip- 
ping of  the  ventricles  over  the  blood  in  the  auricles  in  ventri- 
cular diastole,  due  to  the  aortic  pull. 

THE  INFLUENCES  WHICH  INITIATE  AND  MAY  MOD- 
IFY THE  BEAT  OF  THE  HEART. 

The  cardiac  beat  is  an  automatic  action  and  may  be  carried 
on  in  a  normal  manner  by  the  excised  organ. 


—40— 

The  impulse  to  activity  is  discharged  rhythmically,  prob- 
ably from  certain  nerve  centres  within  the  substance  of  the 
heart..  In  some  animals  the  heart  muscle  itself  has  auto- 
matic contractility. 

The  rate  and  nature  of  the  beat  are  profoundly  modified 
by  various  secondary  influences.  The  following  are  the  sec- 
ondary influences  which  may  be  shown  to  operate  on  the 
heart,  and  to  their  variation  must  be  due  any  alteration  in  the 
character  and  rhythm  of  the  automatic  beat: — 

1.  The  intra-cardiac  blood  pressure.  The  diastolic  intra- 
cardiac pressure  depends  upon  the  volume  of  blood  which 
flows  into  the  heart.  The  systolic  intra-cardiac  pressure 
depends  upon  the  resistance  to  the  flow  of  blood  from  the 
heart,  or  upon  the  blood  pressure  within  the  aorta  and  pul- 
monary artery. 

2.  The  temperature  of  the  blood  entering  the  heart. 

3.  The  chemical  constitution  of  the  blood  supplying  the 
heart. 

4.  The  efferent  nerves  reaching  the  heart  from  extra-car- 
diac centres. 

THE  IlSTFLUEIfCE   UPON"  THE  HEAKT-BEAT   OF   IJTTRA- 
CAEDIAC  BLOOD  PRESSURE. 

The  heart  of  the  frog,  cut  out  from  the  body  and  empty, 
beats  very  feebly  and  comes  to  rest  after  a  while ;  pass  through 
its  cavities  a  weak  saline  solution  under  pressure  and  the 
beats  become  much  stronger  or  go  on  again  for  a  time.  Dis- 
tension of  the  cardiac  ivall  is  a  stimulus  to  the  activity  of  the 
heart.  The  effect  is  more  striking  and  lasting  if  blood 
instead  of  salt  solution  be  used. 

When  the  excised  heart  is  normally  beating  with  an  artifi- 
cial supply  of  blood,  neither  variation  of  arterial  pressure 
nor  variation  of  venous  pressure  produces  any  definite  alter- 
ation in  the  rhythm  of  the  heart-beat.  The  rhythm  of  the 
heart-beat  is  not  directly  affected  by  changes  of  intra-cardiac 
pressure. 


—41— 

The  Avork  done  hy  the  heart  and  the  force  of  its  beat 
increase  with  iutra-cardiac  l)lood-pressure. 

The  normal  heart  is  at  any  moment  able  to  accomplish 
much  more  work  than  it  is  required  to  do. 

IXFLUEXCE    OF    THE    TEMPEIIATUKE    OF    THE    BLOOD 
ENTERING  THE  HEART. 

The  heart  muscle  is  extremely  susceptible  to  changes  of 
temperatui'e.  The  rhythm  of  the  beat  is  uniformly  quicker 
with  a  higher,  and  slower  with  a  lower  temperature.  Changes 
in  the  temperature  of  the  l)lood  amounting  to  a  fraction  of  a 
degree  alter  the  rhythm  of  the  mammalian  heart-beat. 

INFLUENCE  OF  THE  CHEMICAL  CONSTITUTION  OF  THE 
BLOOD  SUPPLYING  THE  HEART. 

The  heart  is  remarkably  insensitive  to  deterioration  in  the 
nutritive  fluid  supplying  it.  The  action  of  the  frog's  heart 
under  minute  quantities  of  nutritive  material.  The  beat  of 
the  isolated  mammalian  heart  supplied  by  blood  poor  in  oxy- 
gen and  rich  in  waste  matters. 

But  the  heart  is  very  sensitive  to  the  action  of  certain 
drugs.  Certain  of  these  affect  the  muscle  of  the  heart 
du'ectly,  others  operate  on  various  parts  of  its  intrinsic  ner- 
vous mechanism. 

The  action  of  alkali  on  the  heart  muscle. 

The  action  of  acid  on  the  heart  muscle. 

The  action  of  digitalin  on  the  heart  muscle. 

The  action  of  atropin  on  the  nervous  mechanism. 

The  action  of  muscarin  on  the  nervous  mechanism. 

THE  INFLUENCE  OF  EFFERENT  NERVES  REACHING 
THE  HEART  FROM  EXTRA-CARDIAC  CENTRES. 

Modifications  of  the  heart-beat  are  probably  normally 
nearly  altogether  due  to  impulses  proceeding  along  the  heart 
nerves.  The  cardio-iiihibifoi'ij  nerve: — fibres  arising  from  the 
spinal  accessory  nerve  join  the  pneumogastric  trunk  within 


—42 — 

tlie  skull  and  are  given  off  from  this  nerve  again  in  the  neigh  - 
borhood  of  the  heart.  Stimulation  of  the  peripheral  end  of 
the  cut  vagus  causes  slowing  of  the  heart-beat  if  the  stimu- 
lation be  weak,  stops  the  beat  if  stimulation  be  strong. 

The  inhibition  due  to  stimulation  is  preceded  by  a  latent 
period  of  one  or  two  heart-beats. 

Exhaustion  of  the  inhibitory  fibres:  after  being  brought  to 
a  standstill,  the  heart  soon  commences  to  beat  again  though 
the  stimulation  be  kept  up. 

Evidence  for  the  constant  action  of  the  vagus-inhibitory 
fibres  upon  the  heart. 

The  vagus  probably  contains  two  other  separate  sets  of 
fibres  whose  action  in  the  one  case  strengthens,  in  the  other 
causes  weakening  of  the  heart-beat,  without  alteration  of  its 
rhythm.  Evidence  derived  from  the  heart  of  the  frog  and 
terrapin. 

The  cardiac  accelerator  &)res  arise  from  the  spinal  cord  and 
reach  the  heart  through  the  last  cervical  and  first  thoracic 
sympathetic  g'engiia. 

Effect  of  stimulating  the  peripheral  end  of  the  spinal  cord 
divided  in  the  neck,  or  the  peripheral  ends  of  the  divided 
accelerator  fibres. 

The  heart-beat  is  quickened  by  the  stimulation.  The  stim- 
ulus required  is  much  stronger  than  for  the  inhibitory  nerve. 
The  latent  period  is  long,  and  the  effect  of  the  stimulation  per- 
sists for  some  time  after  the  cessation  of  the  latter. 

When  the  cardio-inhibitory  and  the  accelerator  fibres  are 
simultaneously  stimulated,  the  heart  is  brought  to  a  stand- 
still as  if  the  vagus  alone  were  irritated. 

PHYSIOLOGICAL   CONDITIONS    WHICH  MODIFY  THE 
HEART-BEAT. 

Emotions  may  operate  on  the  extra-cardiac  heart-centres  so 
as  to  cause  a  change  in  both  rate  and  character  of  heart- 
beat, 


-43— 

Incrensf^.  of  l)lo()d-pressnre  in  the  brain  stimulates  tJie  car- 
dio-inliibitory  centres  directly. 

Increase  of  general  artei-ial  blood-i)ressnre  ])robably  slo^\•s 
the  heart-beat  rellexly. 

Diminution  of  l)lood-pressure  in  the  brain  directly  stimu- 
lates the  cardio-accelerator  centres. 

The  intimate  reflex  association  between  the  heart  and  the 
digestive  tract. 

THE  AUTOMATICITY  OF  THE  HEART. 

The  phenomena  offered  by  the  frog's  heart  when  it  is  cut  in 
different  directions  and  when  its  various  parts  are  separated 
from  each  other. 

The  graded  automaticity  of  the  different  parts  of  the  heart; 
the  decline  of  physiological  resistance  to  discharge  from  the 
venous  sinus  to  the  ventricle. 

The  isolated  ventricle  of  the  frog's  heart  does  not  beat  spon- 
taneously, but  rhythmic  beats  follow  when  it  is  distended  with 
fluid. 

The  function  of  the  ventricles  is  to  drive  the  blood  respect- 
ively in  its  pulmonary  and  systemic  circulation. 

The  functions  of  the  auricles  are,  by  the  frequency  and 
character  of  their  pulsations,  to  regulate  the  rate  and  charac- 
ter of  the  ventricular  contraction.  By  their  beat  to  complete 
the  closure  of  the  auriculo-ventricular  valves;  to  serve  as  a 
store-house  for  blood  during  ventricular  systole. 

The  law  for  the  contraction  of  cardiac  muscle: — Unlike  the 
skeletal  muscles,  cardiac  muscle  refuses  to  give  sub-maximal 
contractions  on  applying  weaker  stimuli. 

The  heart's  contraction  is  probably  not  a  tetanus,  but  along- 
continued  single  contraction. 

The  action  current  of  the  heart. 

THE  APEX  BEAT  AND  THE  SOUNDS  OF  THE  HEART. 

The  apex  beat  felt  outside  the  chest  wall  lasts  thoroughout 
the  systole  of  the  ventricle  and  is  due  to  this.    The  impulse  is 


—44-^ 

due  probably  not  to  a  blow  of  the  heart's  apex  against  the 
chest  wall,  but  simply  to  the  hardening  of  the  heart  muscle. 

The  two  sounds  of  the  heart;  the  time  of  their  occurrence 
in  the  cardiac  cycle  and  their  difference  of  quality. 

The  first  sound;  probably  both  muscular  and  valvular  in 
origin. 

The  second  sound  ;  due  to  the  snapping  to  of  the  semilu- 
nar valves. 

THE  CIRCULATION  OF  THE  BLOOD. 

Proof  that  the  work  power  of  the  heart  is  sufficient  to  com- 
plete the  circulation  of  the  blood.  , 

Rate  of  circulation;  the  blood  completes  its  circuit  from 
ventricle  to  ventricle  in  man  in  about  23  seconds. 

The  area  of  the  arterial  vascular  bed  increases  from  the 
heart  to  the  capillaries  and  then  decreases  in  the  veins  to  the 
heart.  The  flow  of  blood  is  slowest  where  it  passes  through 
the  greatest  area,  that  of  the  capillaries.  The  sum  of  the 
areas  of  cross-section  of  the  systemic  capillaries  is  probably 
eight  hundred  times  as  great  as  that  of  the  aorta. 

The  circulation  of  the  blood  as  observed  in  a  frog  under 
the  microscope.  The  comparison  of  the  flow  in  arteries,  cap- 
illaries and  veins. 

The  "axial"  current;  the  "inert"  layer;  the  respective 
movements  of  white  and  red  corpuscles. 

The  changes  in  the  circulation  brought  about  by  the  pro- 
cess of  inflammation. 

THE  HYDKAULICS  OF  THE  CIECULATOIK. 

The  agents  concerned  in  the  circulation; — (1)  an  incom- 
pressible fluid;  (2)  A  pump  of  intermittent  action;  (3)  A 
set  of  elastic  tubes. 

If  an  artery  be  cut  across  there  is  a  continuous  flow  of 
blood  from  its  central  end  with  an  increased  spurt  at  each 
heart-beat.  Cut  across  a  vein  and  there  is  a  steady  flow  of 
blood  without  pulsation  from  its  peripheral  end. 


—45— 

If  a  mercury  manometer  be  attached  to  an  artery  of  a  liv- 
ing animal  the  position  of  the  mercury  will  show  that  the 
blood  in  the  artery  is  under  considerable  pressure,  the  blood- 
l))-('sstir(',  which  fluctuates  with  each  beat  of  the  heart. 

If  a  manometer  be  attached  to  a  vein  the  mercury  will 
show  a  very  small  blood-pressure  and  no  pulsations. 

Consider  the  causes: — (1)  of  the  high  arterial  and  low 
venous  blood-pressure;  (2)  of  the  continuous  flow  of  blood 
brought  about  by  the  intermittent  action  of  the  pump;  (3)  of 
the  loss  of  the  pulse  in  the  veins. 

The  law  of  the  fall  of  fluid-pressure  in  a  tube  offering 
equal  resistance  to  flow  in  all  its  parts. 

Weber's  schema. 

The  minor  arterial  schema. 

The  major  arterial  schema. 

The  resistance  to  the  movement  of  the  blood  is  internal; 
that  is,  due  to  the  friction  of  the  fluid  particles  against  each 
other.  Conditions  determining  internal  and  external  fi'iction 
in  the  movements  of  fluids. 

The  internal  friction  increases  fast  as  the  calibre  of  the 
vessels  decreases ;  hence  the  chief  resistance  to  the  circulation 
is  in  the  capillaries,  or  is  peripheral. 

Because  of  the  peripheral  resistance  the  arterial  walls  are 
stretched  by  the  blood  pumped  from  the  heart,  and  the 
strained  wall  reacting  on  the  fluid  produces  the  high  arterial 
pressure. 

The  arterial  walls  being  kept  constantly  stretched,  they 
squeeze  constantly  upon  the  inclosed  fluid;  hence  the  flow 
from  a  cut  artery  is  continuous. 

If  the  heart  stop,  the  circulation  continues  to  go  on  until 
the  arteries  have  come  to  a  condition  in  which  they  are  not 
stretched. 

The  hlood-pressure  is  the  immediate  cause  of  the  circu- 
lation. The  action  of  the  heaii  is  its  ]-('mote  cause  and  oper- 
ates through  keeping  the  arteries  stretched  by  forcing  into 
them  fresh  quantities  of  fluid. 

6 


The  energy  o!  the  blood-pressure  is  used  up  in  overcoming 
resistance  to  the  circulation,  and  as  the  chief  resistance  is 
offered  by  the  capillaries,  there  is  a  sudden  fall  of  pressure 
between  the  arteries  and  the  veins. 

Each  new  quantity  of  fluid  thrown  into  the  base  of  the 
aorta  distends  the  vessel  there,  and  this  distension  runs  along 
the  artery  as  the  j^^ilse-wave. 

The  rate  and  height  of  the  pulse-wave  depend  upon  the 
elastic  qualities  of  the  arterial  wall. 

The  pulse-wave  started  at  any  systole  of  the  heart  travels 
much  faster  than  the  blood  whose  entrance  into  the  aorta 
caused  it. 

The  energy  of  the  pulse-wave  is  used  up  in  stretching  the 
vascular  wall;  hence  the  height  of  the  wave  decreases  from 
the  heart  outwards. 

Primary  and  secondary  pulse-waves. 

Study  of  sphygmographic  tracings. 

The  veins  alone  could  contain  all  the  blood  of  the  body. 
The  arteries  are  overfull. 

THE  USE  OF  AETERIAL  ELASTICITY. 

A  greater  amount  of  fluid  is  forced  by  a  pump  in  a  given 
time  through  an  elastic  tube  than  through  a  rigid  one  of  the 
same  calibre. 

The  energy  of  the  heart's  systole  is  stored  in  the  arterial 
wall,  and  acts  throughout  the  cardiac  cycle  as  driving  force  of 
the  blood.  By  this  means  the  useful  energy  of  the  heart  is 
not  limited  in  time  to  its  systole,  but  is  distributed  through  the 
whole  cardiac  cycle.  Consider  the  analogy  of  many  artificial 
machines.  Consider  the  results  to  the  heart  and  the  circula- 
tion of  the  arteries  being  rigid  tubes. 

All  the  energy  of  motion  that  is  lost  to  the  blood  in  circu- 
lation reappears  as  heat  and  goes  to  warming  the  tissues. 


—47— 

As  the  arterial  l)lood-pressure  is  tlie  force  Avliicli  drives  the 
blood  round  its  circuit,  it  is  of  vital  importance  to  the  animal 
that  a  pretty  constant  mean  pressure  be  maintained. 

MEANS  BY  WHICH  ARE  REGULATED  THE  GENERAL 
BLOOD-PRESSURE  AND  LOCAL  BLOOD  SUPPLY. 

The  factors  which  determine  tiie  power  of  the  blood-pres- 
sure are  three: — (1)  The  force  and  frrquency  of  the  heart 
beat  as  determining  the  quantity  of  blood  pumped  into  the 
arteries.  Other  things  being  equal,  blood  pressure  increases 
with  the  quantity  of  blood  forced  out  of  the  heart  in  a  given 
time. 

(2)  The  peripheral  resistance;  arterial  pressure  increases 
and  venous  pressure  proportionately  decreases  as  the  peri- 
pheral resistance  becomes  greater,  other  factors  remaining 
the  same. 

(3)  The  elasticity  of  the  arteries;  other  things  remaining 
equal,  blood-pressure  increases  with  increase  of  elasticity,  or 
resistance  to  distension,  of  the  arterial  walls. 

Inhibition  of  the  heart's  action  through  stimulation  of  the 
vagus  nerve  causes  a  sudden  fall  of  blood-pressure. 

Quickening  of  the  heart's  action  by  stimulation  of  the 
accelerator  nerves  does  not  alter  the  blood-pressure. 

THE   VASO-MOTOK   EEGUL ATION   OF   BLOOD-PRESSURE. 

Withdrawal  of  a  large  quantity  of  blood  from  an  animal 
does  not  loAver,  except  momentarily,  the  blood-pressure. 

The  injection  of  a  large  quantity  of  foreign  blood  into  the 
vessels  of  an  animal  produces  no  permanent  rise  of  blood- 
pressure. 

When  the  spinal  cord  of  an  animal  is  divided  in  the  neck 
the  mean  arterial  blood-pressure  decreases  to  a  small  fraction 
of  its  former  value.  When  the  peripheral  end  of  the  cut 
cord  is  stimulated  arterial  pressure  rises  again.  Both  the  fall 
and  the  rise  of  pressure  are  somewhat  gradual. 

The  vaso-motor  centres  in  the  medulla  oblongata. 


—48— 

Efferent  impulses  proceed  from  the  vaso-motor  centre  along 
vaso-motor  nerves  to  all  parts  of  the  body,  and  keep  the  mus- 
cular coats  of  the  small  arteries  and  arterioles  in  a  state  of 
tonic  contraction,  thus  increasing  the  peripheral  resistance  to 
the  flow  of  blood. 

Secondary  vaso-motor  centres  in  parts  of  the  brain  other 
than  the  medulla  oblongata,  and  in  the  spinal  cord. 

It  is  not  proven,  but  is  not  improbable,  that  the  capillaries 
are  under  vaso-motor  control. 

The  experiment  of  cutting  and  stimulating  the  cord  of  a 
frog  while  its  circulation  is  observed  under  the  microscope. 

THE  EEGULATION  OF  LOCAL  BLOOD  SUPPLY. 

The  various  organs  of  the  body  require  an  increase  of  blood 
supply  during  their  periods  of  activity  and  a  lesser  quantity  in 
the  intervals  between. 

Stimulation  of  sympathetic  nerve  branches  supplying  any 
area  nearly  always  produces  contraction  of  the  vessels  in  that 
area. 

Efferent  vaso-dilator  as  distinguished  from  vaso-consfrictor 
nerves. 

The  vaso-motor  effect  of  stimulating  the  peripheral  end  of 
the  mylo-hyoid  nerve  in  the  frog. 

The  effect  of  stimulating  the  peripheral  end  of  the  chorda 
iympani  upon  the  circulation  in  the  sub-maxillary  gland  of 
the  dog. 

The  physiology  of  blushing. 

The  functional  vaso-motor  changes  of  erectile  tissues. 

The  changes  in  the  circulation  of  a  vascular  area  on  stimu- 
lating its  vaso-dilator  nerve:  The  increased  calibre  of  the 
arterioles;  the  more  rapid  blood  current;  the  flow  of  red 
blood  through  the  veins;  the  venous  pulse. 

The  evidence  for  the  presence  in  the  medulla  of  a  double 
vaso-motor  centre,  one  part  sending  out  vaso-constrictor 
nerves,  the  other  part  supplying  vaso-dilator  nerves.  When 
one  organ  receives  more  or  less  blood  than  usual,  there  must 


-49— 

be  an  alteration  of  vaso-motor  tone  in  the  blood-vessels  of 
other  districts  in  order  tiiat  the  mean  ])lo()d-prcssure  shall 
remain  constant. 

Local  paralysis  of  vaso-motor  mechanism. 

The  influence  of  temperature  and  of  mechanical  disturbances 
on  vaso-motor  activity. 

Gradual  recovery  of  vascular  tone  in  any  area  after  cutting 
off  its  vaso-motor  nerves. 

The  relation  of  the  sympathetic  ganglia  to  vaso-motor  tone. 

THE   REFLEX  EXCITEMENT  OF  THE  VASO-MOTOR  CEN- 
TRES. 

Stimulation  of  the  central  end  of  nearly  any  sensory  nerve 
produces  general  reflex  vaso-motor  constriction  and  a  conse- 
quent rise  of  blood-pressure. 

The  function  of  the  depressor  nerve,  which  in  the  cat  and 
rabbit  finds  its  way  to  the  heart  in  a  path  independent  of  the 
vagus.  The  depressor  is  an  afferent  nerve;  when  divided, 
stimulation  of  its  central  end  brings  about  a  fall  of  blood 
pressure  without  marked  change  in  the  pulse-rate,  provided 
the  vagi  be  cut. 

The  fall  of  blood-pressure  is  due  to  reflex  dilation  of  the 
abdominal  vessels. 

The  reflex  dilatation  of  the  vessels  in  a  rabbit's  ear  through 
stimulation  of  the  great  auricular  nerve. 

The  reflex  dilatation  of  the  blood  vessels  of  glands  due  to 
the  stimulating  effect  of  food  upon  the  appropriate  mucous 
membranes. 

Remembering  that  arterial  pressure  is  the  driving  force  of 
the  blood,  consider  the  difference  of  physiological  effect 
between  rapidly  drawing  a  certain  amount  of  blood  from  an 
artery  and  from  a  vein. 

THE  LYMPHATIC  VESSELS  AND  THE  FLOW  OF  LYMPH. 

Two  modes  of  origin  of  lymphatic  vessels; — plexiforni  and 
lacunar. 


—50- 

The  relative  size  and  direction  of  lymph  and  blood  capil- 
laries. 

The  thin  vein-like  walls  of  lymphatic  vessels;  their  numer- 
ous valves. 

The  stoniafa.  of  serous  membranes. 

Every  tissue  element  probably  lies  in  a  lymphatic  space 
from  which  fluid  rapidly  reaches  lymphatic  channels. 

The  direction  of  flow  in  the  lymphatic  vessels. 

Influences  modifying  the  flow  of  lymph ; — muscular  action ; 
position  of  the  body;  respiratory  movement.  Flow  from  the 
opened  thoracic  duct  of  a  dog. 

The  lymphatic  hearts  of  birds,  reptiles  and  batrachians. 

Difference  between  lymph  and  chyle. 

Lymphatic  glands ;  their  position,  structure  and  function. 

The  general  purpose  and  cause  of  the  existence  of  lymph. 

DEMONSTRATIONS. 

Comparison  of  the  elasticity  of  arteries  and  veins. 

The  valves  in  the  veins. 

Dissection  of  a  sheep's  heart. 

Artificial  circulation  through  a  sheep's  heart. 

The  movement  of  needles  in  the  mammalian  heart. 

The  beat  of  the  isolated  heart  with  an  artificial  supply  of 
blood. 

The  influence  upon  the  beat,  of  variable  pressures;  of  tem- 
perature changes;  of  various  drugs. 

The  rhythm  of  beat  in  the  isolated  heart  of  the  frog. 

The  beat  of  the  mammalian  heart  directly  observed. 

The  behavior  of  the  ganglion  free  apex  of  the  frog's  heart. 

Yagus  inhibition  of  the  heart-beat  in  a  frog. 

The  minor  arterial  schema. 

Weber's  schema. 

Major  arterial  schema. 

Schema  of  vaso-motor  regulation. 

Comparison  of  blood-pressures  in  the  carotid  and  femoral 
arteries  of  a  mammal.     Effect  on  the  blood-pressure  of  vagus 


—51— 

stimulation.  The  graphic  method  of  recording  physiological 
observations. 

Comparison  ot*  the  blood-pressure  and  its  fluctuations  in 
the  femoral  vein  and  femoral  artery. 

The  effect  upon  blood-pressure  of  stimulatng  the  depressor 
nerve. 

The  efPect  upon  blood-pressure  of  cutting,  and  then  stimu- 
lating the  spinal  cord. 


X.  THE  RESPIRATION. 

THE  RESPIRATORY  MECHANISM  AND  ITS  FUNCTIONS. 

The  object  of  tlie  respiration  is  the  removal  from  the  body 
of  waste  products  of  tissue  change  and  the  renewal  of  oxy- 
gen to  the  tissues. 

This  interchange  of  matter  is  brought  about  by  the  process 
of  diffusion. 

The  function  of  respiratory  movement  is  to  hasten  the  pro- 
cess of  diffusion. 

The  modification  of  the  respiratory  apparatus  in  different 
animals.  Respiration  in  the  amoeba ;  in  a  marine  ivorm  ;  in  a 
fish  ;  in  an  insecf ;  in  &.fi'og  ;  in  a  mammal. 

THE  STRUCTURE  OF  THE  RESPIRATORY  ORGAKS  IN  MAN. 

The  trachea  and  bronchi ;  the  incomplete  cartilaginous 
rings  ;  the  mucous  glands  ;  the  ciliated  epithelium. 

The  lungs  ;  the  lung  alveoli ;  the  air-cells  and  their  flattened 
lining  epithelium  ;  the  capillary  circulation  in  the  lung. 

Comparison  of  the  lungs  of  the  batrachian,  reptile  and 
mammal. 

The  muscular  and  elastic  tissue  of  the  lung. 

The  topographical  relations  of  the  lungs.     The  pleura. 

Functions  of  the  cilia  in  cleansing  the  air  passages  and 
aiding  in  the  mixture  of  gases. 

THE  MOVEMENTS  OF  RESPIRATION. 

The  lungs  are  extremely  elastic  and  extensible.  They  are 
but  semi-distended  in  the  thorax.  The  pressure  exerted  by 
the  elasticity  of  the  lungs  in  man  is  about  that  of  a  column 
of  mercury  five  milimetres  high. 

7 


--54— 

The  atmospheric  pressure  upon  the  inside  o£  the  lungs 
keeps  them  distended  while  in  the  closed  chest. 

When  the  chest  cavity  is  enlarged  in  inspiration  the  atmos- 
pheric pressure  causes  the  lungs  to  fill  the  new  space  ;  and 
when  the  cavity  becomes  smaller  in  expiration  the  elasticity 
o£  the  lung  substance  causes  a  corresponding  diminution  in 
the  bulk  of  the  lungs. 

Demonstration  on  an  artificial  schema  and  on  a  rabbit  of 
the  effects  of  the  respiratory  movements  upon  the  contents  of 
thejchest. 

In  ordinary  breathing  inspiration  only  involves  muscular 
effort,  the  expiration  being  performed  by  the  elastic  reaction 
of  the  parts. 

The  cavity  of  the  chest  is  increased  vertically  by  the  con- 
traction of  the  muscle  of  the  diaphragm.  The  effect  of  violent 
contraction  of  the  diaphragm  upon  the  lower  ribs  and  upon  the 
abdominal  viscera. 

The  lateral  increase  of  the  chest  cavity  due  to  contraction 
of  the  diaphragm. 

The  movements  of  the  ribs  and  sternum  in  respiration. 

The  exieiiial  intercostals,  the  scaleni  and  the  levaioi'es  cos- 
tarum  are  the  elevators  of  the  ribs  in  ordinary  inspiration. 

Consider  the  adaptation  of  shape  and  position  of  the  ribs 
and  costal  cartilages  to  the  purposes  of  respiration. 

In  labored  inspiration  the  following  muscles  are  also  called 
into  play:  Scrrcdus  magniis,  peciorfdis  minor,  pedoralis  ma- 
jor, l(dissimus  dorsi,  serrcdus  posticus  su'peiior,  serrcdus pos- 
ticus inferior,  qua.dndus  lumborum,  sacro-lumbalis. 

The  internal  intercostals  are  probably  muscles  of  ordinary 
expiration. 

In  labored  expiration  the  abdominal  muscles  are  the  chief 
active  agents. 

The  action  of  the  intercostal  muscles  as  illustrated  on  Bam- 
berger's schema. 

In  the  human  species  costal  respiration  is  relatively  most 
marked  in  the  female,  abdominal  respiration  in  the  male. 


—55— 

Th  e  movements  of  the  face  and  larynx  in  respiration. 
The  rhythm  of  respiration. 

THE    QUANTITY   OF    AIR    IN    THE    LUNGS    AND    ITS 

VARIATION. 

After  the  most  violent  expiration  the  lungs  still  contain 
about  100  cubic  inches  of  air,  called  th-  residual  air.  At  the  end 
of  an  ordinary  expiration  tlie  lungs  contain  an  additional  100 
cubic  inches  of  sujyplcnwidcd  air.  Thus  there  are  200  cubic 
inches  of  shdioiiarij  air  which  in  ordinary  breathing  never 
leave  the  chest.  In  ordinary  inspiration  an  additional  30  cubic 
inches  of  tidal  air  are  drawn  in.  By  a  forced  inspiration  there 
may  still  be  added  about  93  cubic  inches  of  complemcnffd  air. 
The  full  capacity  of  the  lungs,  then,  is  328  cubic  inches;  the 
vital  capacd/j,  the  amount  of  air  capable  of  being  taken  in 
after  the  most  powerful  expiration,  is  228  cubic  inches.  These 
capacities  are  estimated  from  the  lungs  of  a  man  of  medium 
size. 

The  process  of  gas  interchange  in  the  lungs  under  these 
conditions. 

The  quantity  of  air  breathed  daily. 

The  effect  of  respiration  upon  the  movement  of  blood  and 
lymph. 

THE  CHANGES  OF  AIR  IN  RESPIRATION. 

The  air  expired  is  nearly  always  warmer  than  that  inspired. 

About  five  per  cent,  of  the  heat  lost  to  the  body  goes  to 
warming  the  expired  air,  and  about  15  per  cent,  is  employed  in 
evaporating  the  water  of  respiration. 

The  air  expired  is  nearly  saturated  with  moisture. 

Pure  dried  air  contains  in  100  vols. 
Expired  air  contains  in  100  vols. 

The  expired  air  also  contains  small  but  important  quanti- 
ties of  volatile  organic  matters. 


Dxygen. 

Nitrogen. 

Carbonic  Aci' 

20.81 

79.15 

.04 

16.033 

79.557 

4.38 

—56— 

The  volume  and  weight  of  oxygen  absorbed  and  carbonic 
acid  given  off  in  a  day. 

Owing  to  its  higher  temperature  and  contained  watery 
vapor  the  volume  of  air  expired  is  greater  than  that  inspired; 
but  when  dried  and  measured  at  the  same  temperature  the  air 
inspired  is  found  to  have  diminished  in  bulk,  having  lost  a 
greater  volume  of  oxygen  than  it  has  gained  of  carbonic  acid 
in  respiration. 

Ventilation.  The  hurtful  qualities  of  air  which  has  been 
respired  are  due  not  so  much  to  its  carbonic  acid  as  to  the 
animal  matter  contained  in  it. 

THE  CHANGES  UNDERGONE  BY  THE  BLOOD  IN  THE 

LUNGS. 

The  losses  and  gains  of  the  blood  in  the  lungs. 

The  difference  in  color  between  the  venous  and  arterial 
blood. 

When  exposed  to  a  vacuum  100  vols,  blood  give  off  about 
72  vols,  gas,  measured  at  O'^C.  and  750  millimetres  pressure. 

Oxygen.      Carbonic  acid.     Nitrogen. 

ino  vols  ^^^erial  blood    .  20  50  2 

100  vols.  Yeno^^g  ^i^^^i  give  ^q  ^q  2 

The  color  of  the  blood  of  an  asphyxiated  animal. 

The  color  of  the  blood  is  due  to  the  haemoglobin  contained 
in  the  red  corpuscles. 

Oxyhsemoglobin  and  reduced-hsemoglobin.  Hsemoglobin 
crystals. 

Poisoning  by  carbon  monoxide  gas. 

The  spectroscopic  study  of  hsemoglobin  and  its  derivatives. 

The  amount  of  gas  given  off  to  a  vacuum  by  blood  is  greatly 
in  excess  of  that  which  could  be  obtained  from  an  equal  vol- 
ume of  blood  serum. 

The  laws  which  govern  the  absorption  of  gases  by  liquids. 

The  explanation  of  the  large  quantity  of  gas  found  in  blood 
is  the  chemical  union  of  the  oxygen  with  the  hsemoglobin. 

The  combination  of  oxygen  with  hsemoglobin  is  not  a  stable 


—57— 

one,  but  the  gas  is  given  off  when  the  partial  pressure  of  oxy- 
gen upon  the  blood  falls  below  one  inch  of  mercury. 

Comparison  of  the  partial  pressures  of  gases  in  the  lung 
alveoli  and  in  the  blood. 

The  carbonic  acid  of  the  blood  exists  chiefly  in  loose  chemi- 
cal combination  with  substances  in  the  plasma. 

The  respiration  of  the  tissues.  The  same  laws  determine 
the  gas  interchange  in  the  tissues  as  in  the  lungs. 

The  blood  in  the  left  side  of  the  heart  is  cooler  than  that  in 
the  right  side  because  more  heat  is  lost  to  the  blood  in  the 
lungs  than  is  gained  by  the  oxidation  of  hsemoglobin. 

The  ratio  of  the  amount  of  oxygen  absorbed  and  of  carbonic 
acid  given  off  by  the  tissues  in  a  certain  time  is  not  constant. 
During  the  day  more  oxygen  is  given  off  in  carbonic  acid  than 
is  taken  up  in  the  same  time;  during  the  night  the  propor- 
tions are  reversed.  The  same  relation  holds  for  periods  of 
activity  and  of  rest. 

The  amount  of  oxygen  taken  into  the  blood  depends  not 
upon  the  amount  supplied  to  the  lungs  but  upon  the  amount 
which  has  been  used  by  the  tissues.  The  haemoglobin  of  ar- 
terial blood  is  normally  nearly  or  quite  saturated  with  oxygen. 
The  erroneous  idea  that  respiration  of  pure  oxygen  acceler- 
ates the  oxidations  of  the  body. 

The  oxidations  of  the  body  occur  not  in  the  blood  but  in  the 
tissues. 

The  history  of  the  physiology  of  respiration. 

THE  NERVOUS  MECHANISM  OF  THE  RESPIRATION. 

The  mixed  voluntary  and  involuntary  characters  of  the  re- 
spiratory movements. 

The  respiratory  centre  in  the  medulla  oblongata.  Instant 
cessation  of  respiratory  movement  follows  destruction  of  this 
centre. 

The  phrenic  nerves  spring  from  the  spinal  cord  at  about 
the  level  of  the  4th  pair  of  cervical  nerves;  the  intercostal 
nerves  leave  the  cord  throughout  the  dorsal  region. 


—58— 

The  modified  respiratory  movements  producing  speech,  etc. 
The  co-ordination  of  the  various  respiratory  movements. 
The  effect  upon  the  movement  of  cutting  a  nerve  supplying 
any  part  of  the  respiratory  apparatus. 

THE  CONDITIONS  UNDER  WHICH  THE  RESPIRATORY 
CENTRE  ACTS. 

The  movements  of  respiration  are  remarkably  susceptible 
to  modification  under  the  influence  of  stimuli  foreign  to  their 
nervous  centre;  effect  of  a  dash  of  cold  water;  effect  of  emotions. 

When  any  single  efferent  respiratory  nerve  is  cut  the  part 
supplied  by  it  remains  quiescent;  and  when  the  spinal  cord  is 
divided  below  the  medulla  the  failure  in  the  income  of  oxygen 
is  accompanied  by  an  exalted  action  of  the  respiratory  centre 
as  shown  by  the  more  powerful  action  of  the  remaining  respir- 
atory movements  of  the  mouth  parts,  though  these  are  ineffi- 
cient to  aerate  the  blood. 

When  the  vagi  are  divided  on  each  side  of  the  neck  the 
respiratory  movements  become  slower  and  deeper,  but  do  not 
cease. 

When  the  central  end  of  the  cut  vagus  is  gently  stimulated 
the  respiration  is  quickened,  and  it  may  be  so  hastened  that 
the  respirations  are  fused  together  and  the  muscles  come  to  a 
tetanic  standstill  in  the  phase  of  inspiration. 

When  the  central  end  of  a  superior  laryngeal  nerve  is  stim- 
ulated the  respiration  becomes  slower  and  deeper,  and  if  the 
stimulus  be  sufficiently  strong  expiratory  tetanus  is  produced. 

The  same  is  true,  but  to  a  slighter  extent,  of  the  inferior 
laryngeal  nerve. 

It  is  not  improbable  that  the  mere  mechanical  conditions  of 
the  lung  in  the  phases  of  expiration  and  inspiration  excite  the 
respective  movements  of  inspiration  and  expiration. 

It  is  clear,  then,  that  the  respiratory  centre  is  under  the 
modifying  control  of  stimuli  proceeding  to  it  along  afferent 
nerves.  But  that  the  essential  activity  of  the  centre  is  quite 
independent  of  any  stimulus  reaching  it  from  without. 


—59— 
THE  EXCITING  CAUSE  OF  THE  RESPIRATORY  MOVEMENT. 

The  action  of  tlie  respiratory  centre  is  determined  by  the 
condition  of  the  blood  supplying  it. 

The  centre  is  made  active  by  venous  blood,  but  is  not  ex- 
cited by  arterial  blood. 

It  ax^pears  to  be  the  want  of  oxygen  and  not  the  excess  of 
carbonic  acid  which  stimulates  the  centre,  as  shown  by  the 
respiratory  disturbance  of  an  animal  breathing  in  an  atmos- 
phere of  hydrogen. 

The  activity  of  the  respiratory  centre  is  determined  l)y  the 
direct  influence  of  the  blood  upon  it,  irrespective  of  the  con- 
dition of  the  blood  in  other  parts  of  the  body. 

We  may  suppose  that  the  activity  of  the  respiratory  centre 
causes  an  accumulation  of  stimulating  waste  products  in  it, 
and  that  the  oxygen  supplied  by  arterial  blood  combines  with 
and  renders  these  inert. 

The  change  of  normal  respiratory  rhythm  into  that  of 
(lyspnoecL 

The  breathing  of  dyspnoea  owes  its  character  to  lack  of 
oxygen.  In  ordinary  dyspnoea  the  breathing  is  deeper  than 
usual  and  the  rhythm  generally  slower,  as  after  section  of  the 
phrenic  nerves.  In  the  dyspnoea  of  asthma,  however,  the 
respirations  are  quicker  and  rather  less  deep  than  usual. 

Physiological  upncea  is  the  condition  of  rest  in  the  respira- 
tory centre  due  to  excessive  respiration. 

THE  RHYTHMIC  ACTION  OF  THE  RESPIRATORY  CENTRE. 

The  respiratory  discharge  is  probably  the  resultant  of  two 
forces,  one  exciting  to  discharge  and  the  other  resisting  it. 
Many  mechanical  anal  ogies  can  be  cited  showing  how,  under 
similar  conditions,  rhythmic  action  is  brought  about. 

The  waste  products  of  tissue  change  in  the  respiratory  cen- 
tre are  probably  the  stimuli  to  its  discharge. 

The  function  of  the  afferent  respiratory  nerves  is  probably 
to  either  increase  or  diminish  the  exciting  as  compared  with 
the  resisting  force  in  the  centre. 


—60— 

The  7'esistance  theor'y. 

The  double  nature  of  the  respiratory  centre  :  the  mspirafonj 
centre;  the  expiraforij  centre. 

The  phenomena  and  means  of  production  of  asphyxia. 

Poisoning  by  carbonic  oxide. 

Modified  respiratory  movements; — yawning;  sighing  \  cough- 
ing; hiccough;  sneezing;  laughing;  sobbing. 

DEMONSTRATIONS. 

Schema  illustrating  the  effect  upon  lungs  and  heart  of  the 
respiratory  movements. 

Hamberger's  schema  illustrating  the  action  of  the  intercos- 
tal muscles. 

Proof  of  the  absorption  of  oxygen  and  the  production  of 
carbonic  acid  in  respiration. 

The  respiratory  rhythm,  and  the  phenomena  of  dyspnoea, 
apncea,  and  asphyxia. 

The  effect  of  stimulating  the  afferent  respiratory  nerves. 

Puncture  of  the  nonud  vital. 


XL    THE  SKIN  AND  ITS  APPENDAGES, 

The  skin  consists  of  two  layers,  an  outer  cellular  layer,  the 
epidermis  or  cuticle,  and  an  inner  layer  composed  chiefly  of 
connective  tissue,  the  deiDiis,  cutis  vera  or  coriiDii. 

The  hairs  and  nails  are  local  modifications  of  the  epidermis. 

HISTOLOGICAL  STRUCTURE  OF  THE  SKIN  AND  ITS 
APPENDAGES. 

The  dermis: — its  structural  tissue;  the  papill* — their  ar- 
rangement in  two  rows;  its  blood  vessels;  tactile  corpuscles 
and  Pacinian  bodies;  groups  of  fat  cells. 

The  epidermis: — soft  and  horny  epidermis ;  the  lower  layer 
of  perpendicular  cells;  the  pigmented  cells  of  dark  races; 
nerve  endings;  cause  of  external  ridges. 

The  nails. 

The  sudoriparous  or  sweat  glands;  the  spiral  opening  and 
the  coiled  inner  termination. 

Hair;  the  papilla  and  hair  follicle;  the  hair  muscles;  the 
erectile  tissue  about  the  base  of  sensory  hairs. 

The  sebaceous  or  oil  glands. 

THE  SECRETION  OF  THE  SWEAT  GLANDS. 

The  functions  of  the  perspiration  are  to  remove  waste  mat- 
ters from  the  body,  and  to  serve  as  a  regulator  of  the  body 
temperature. 

The  conditions  determining  the  amount  of  perspiration : — 
temperature  ;  moisture  of  the  air  ;  exercise  ;  nature  of  food. 

The  quantity  of  sweat  secreted  in  tAventy-four  hours. 

Sensible  and  insensible  perspiration. 

The  sweat  is  acid  in  reaction  and  owes  its  odor  to  volatile  oils. 

Composition  of  the  perspiration; — water;  fatty  acids; 
sodium  chloride;  urea. 

8 


THE  MECHAKISM  OF  THE  SWEAT  SECRETI0;N^. 

An  increased  flow  of  blood  to  the  skin  usually  attends  the 
production  of  perspiration,  but  is  not  the  cause  of  it.  The 
dry  skin  of  fevered  patients. 

The  emotion  of  terror  may  cause  sweating  from  a  pale  skin. 

Sweat  is  produced  by  the  activity  of  the  cells  of  the  sudor- 
iparous glands  under  control  of  the  nervous  system. 

Section  of  the  sciatic  nerve  of  the  cat  causes  reddening  of 
the  balls  of  the  feet,  but  no  sweating.  Stimulation  of  the  per- 
ipheral end  of  the  nerve  causes  the  secretion  to  appear  upon 
the  balls  of  the  feet  even  of  a  freshly  amputated  leg. 

Sweating  as  a  reflex  action. 

Pilocarpin  excites  to  activity  the  sweat  glands;  atropin 
abolishes  their  functions. 

Absorption  by  the  skin. 

The  secretion  of  the  sebaceous  glands. 


XII.  THE  KIDNEYS  AND  THEIR  SECRETION. 

GKOSS  STRUCTUKE  OF  THE  KIDNEY. 

The  capsule  surrounding  and  vessels  entering  the  kidney. 

The  hi  I  lis:  j)('lri><:  enliven.  The  cortical  and  medullary  por- 
tions of  the  opened  kidney;  the  papilbe.  The  pyramids  of 
Malpighi  and  of  Ferrein. 

MICROSCOPIC  STKUCTURE  OF  THE  KIDXEY. 

The  uriniferous  tubules;  the  Malpighian  corpuscles;  the 
loops  of  Henle;  the  convoluted  and  collecting  parts  of  the 
tubules. 

The  lining  cells  peculiar  to  the  different  parts  of  the  tubules. 

The  blood  supply  of  the  kidney;  the  f/loiuei-uh'. 

THE  URINE. 

The  quantity  secreted  in  24  hours  varies  from  40  to  60  fluid 
ounces. 

The  complementary  activity  of  skin  and  kidneys. 
The  color,  reaction  and  specific  gravity  of  urine. 
The  variation  of  color  and  specific  gravity. 

THE  AMOUNT  AND  COMPOSITION  OF  URINE  PASSED  BY  A 
MEDIUM  SIZED  MAN  IN  TWENTY-FOUR  HOURS.  (Foster's 
Physiology.) 

Water 1,500.000  grammes 

Total  solids 72.000  grammes 

Urea 33.180  grammes  Chlorine 7.000  grammes 

Uric  acid 555  grammes  Ammonia 770  grammes 

Hippuric  acid. .        .I:(X)  grammes  Potassium 2.500  grammes 

Pigment  fats,&c    10.000  grammes  Sodium 11,090  grammes 

Sulphuric  acid. .      2.012  grammes  Calcimii 260  grammes 

Phosphoric  acid     3. Ki-l  grammes  Magnesium 207  grammes 


—64— 

The  ash  of  urine  is  nearly  the  same  as  the  inorganic  mat- 
ter directly  determined. 

The  general  nature  and  origin  of  the  various  substances 
found  in  the  urine. 

THE  SECRETORY  MECHANISM. 

The  uriniferous  tubule  consists  of  two  parts,  each  of  which 
probably  serves  special  purposes.  The  thin-walled  capsules 
round  the  glomeruli  probably  allow  rapid  filtration  of  water 
and  salts  through  them,  while  the  cells  lining  the  tubules 
proper  have  no  doubt  the  function  of  active  secretion. 

IN^FLUEIN^CES  DETEEMINING  THE  AMOUNT  OF  THE  SECRE- 
TION. 

Increased  flow  of  blood  to  the  kidney,  bringing  about  a 
high  blood-pressure  in  the  glomeruli,  increases  the  amount  of 
urine  secreted.  This  may  follow  general  rise  of  blood-press- 
ure or  local  dilatation  of  the  renal  arteries. 

The  effect  of  cold  in  constricting  the  vessels  of  the  skin  is 
to  raise  general  blood-pressure. 

Complementary  action  of  skin  and  kidiieys. 

Dilution  of  the  blood  increases  the  secretion. 

Stoppage  of  the  secretion  after  section  of  the  spinal  cord. 

.THE  SECRETORY  EPITHELIUM  OF  THE  TUBULES. 

It  is  probable  that  the  cells  lining  the  tubules  have  the 
power  of  active  secretion  independent  of  blood-flow. 

The  passage  of  indigo-carmine  through  the  renal  cells. 

The  injection  of  urea  or  urates  excites  the  flow  of  urine. 

The  process  of  secretion  as  studied  in  the  kidney  of  an 
amphibian. 

The  distinction  between  selection  by  the  kidney  cells  of 
urea  from  the  blood  and  the  manufacture  of  it  by  them  from 
certain  antecedents. 

The  evidences  as  to  the  part  played  by  the  kidney  cells  in 
the  elimination  of  urea. 

The  physiology  of  micturition. 


—(55— 
DEM0N8T11ATIOXS. 


The  secretion  as  collected  from  the  ureter;  the  efiPect  of 
Ijlood-pressure  upon  the  rate  of  secretion. 

The  effect  of  dilution  of  the  blood  and  of  the  addition  of 
urea  to  it,  upon  the  rate  of  secretion. 


XIII.    THE  PHYSIOLOGY  OF  SECRETION. 

All  the  phenomena  of  secretion  probably  depend  in  the  end 
for  their  occurrence  on  the  physicfd  laws  of  difPusion  and 
filtration. 

The  nature  of  the  laws  regulating  the  diffusion  and  filtra- 
tion of  fluids  and  gases. 

Simple  application  of  the  laws  of  diffusion  in  the  living 
body.  The  production  of  diarrhoea  by  the  j)reseuce  of  mag- 
nesium salts  in  the  intestine.  The  interchange  of  matter 
between  the  lymph  and  the  blood  and  the  relation  of  the 
animal  cell  to  the  process.     The  gas  exchange  in  the  lungs. 

Secretion  is  not  simply  a  process  of  diffusion  and  filtration 
through  dead  membranes.  The  diff'usion  membrane  of  secre- 
tion is  (illve. 

In  the  simplest  form  of  true  secretion  certain  substances 
are  selected  by  and  passed  through  the  secreting  membrane. 
But  most  secreted  fluids  contain  specific  matters  which  have 
been  produced  by  the  vital  activity  of  secretory  cells. 

The  typical  secretory  animal  membrane :  ( 1 )  the  secretory 
cell;  (2)  the  basement  membrane;  (3)  the  capillary  network. 

The  modification  of  the  typical  secretory  membrane  into 
glands. 

Various  forms  of  glands:  tubular  aiid  racemose  glands. 

The  parts  of  a  gland:  the  duct;  the  acinus  or  alveolus. 

The  circulation  in  glandular  tissue. 

Enzyni.     Mucous  and  (iJhiuiiiiious  glands. 

THE  PHENOMENA    OF   SECRETION   AS   DETERMINED 
IN  THE  SUB-MAXILLARY  GLAND. 

The  nerve  supply  of  the  gland,  and  the  processes  of  normal 
secretion. 


-68- 
THE  CHEMICAL  C0:NSTITUTI0N"  OF  SALIVA. 

The  proportions  of  water,  salts,  and  organic  matters.  The 
relative  diffusibility  of  the  constituents.  The  specific  bodies 
of  the  secretion. 

THE  cha:nges  produced  in   the  sub-maxillary 

GLAI^D   BY   STIMULATIJ^G  THE   PERIPHERAL   END   OF 
THE  CHORDA   TYMPANl  NERVE. 

The  dilation  of  the  blood  vessels;  the  venous  pulse  and  red 
blood  in  the  veins.     Yaso-dilator  nerves. 

The  volume  of  fluid  continuously  secreted  may  exceed  that 
of  the  gland;  the  fluid  could  therefore  not  have  been  all  stored 
in  the  resting  gland,  but  must  have  come  from  the  blood  dur- 
ing the  stimulation. 

The  saliva  is  not  simply  filtered  from  the  blood,  for  the 
secretion  still  goes  on  when  the  pressure  of  saliva  within  the 
duct  exceeds  that  of  the  blood  in  the  artery  of  the  gland. 

Fibres  of  the  cliorda  iympani  must  control  the  secretory 
activity  of  the  gland  cells;  for,  after  poisoning  with  atropin, 
stimulation  of  the  choi-<la  still  produces  vaso-motor  dilatation 
in  the  gland,  but  causes  no  secretion. 

The  antagonistic  actions  of  atropin  and  pilocarpin. 

The  watery  fluid  of  the  secretion  must  have  been  contained 
in,  and  actively  forced  out  of,  the  gland  cells. 

The  secretion  obtained  by  artificial  stimulation  from  the 
gland  of  a  decapitated  animal. 

The  chief  volume  of  the  secretion  consists  of  the  easily 
filtered  and  diffusible  water  with  salts  in  solution. 

The  volume  of  fluid  secreted  in  a  given  time  does  not  mark- 
edly diminish  during  a  series  of  stimulations. 

The  organic  matters  of  the  saliva  are  not  readily  diffusible. 

The  organic  matters  decrease  in  quantity  as  secretion  pro- 
gresses. They  are  probably  made  by  and  stored  up  within 
the  gland  cells. 

The  temperature  of  saliva  in  the  gland  duct  is  higher  than 
that  of  the  blood. 


—GO- 
NERVES  WHICH  REGULATE  THE  CHEMICAL  NATURE  OE 
THE  GLAND  CELL  SUBSTANCE. 

When  the  sympathetic  nerve  supplying  the  sub-maxiUaiy 
gLand  of  the  dog  is  stimulated,  the  blood  vessels  of  the  gland 
contract  and  the  amount  of  secretion  is  insignificant  and  is 
viscid  in  consistency.  The  chorda  saliva  is  more  abundant 
and  less  viscid  than  the  syntpathctic. 

Stimulation  of  the  peripheral  end  of  the  nerve  of  Jacobson  in 
the  dog  produces  an  abundant  secretion  from  the  parotid  gland. 

Stimulation  of  the  peripheral  end  of  the  sympathetic  sup- 
plying the  parotid  gland  of  the  dog  causes  no  secretion,  but 
greatly  increases  the  organic  content  of  the  secretion  produced 
by  subsequent  stimulation  of  the  nerve  of  Jacobson. 

Nerves  of  three  distinct  physiological  varieties  can  be  shown 
to  take  part  in  secretion:  (1)  Vaso-mofor  nerves,  which  reg- 
ulate the  calibre  of  the  blood  vessels;  (2)  secretory  nerves, 
which  bring  about  the  active  diffusion  of  water  and  salts 
through  the  gland  cells;  (o)  irophic  nerves,  which  produce 
chemical  changes  in  the  gland  substance,  giving  rise  to  more 
soluble  organic  matters  in  it. 

THE  HISTOLOGICAL  CHANGES  OF  THE  SALIVARY  GLANDS 
IN  SECRETION. 

Comparison  of  the  appearance  and  reaction  toAvard  staining 
reagents  of  a  resting  sub-maxillary  gland  with  one  which  has 
abundantly  secreted. 

Comparison  of  the  histological  characters  of  the  j)arotid 
gland  before  and  after  stimulation  of  the  sympathetic  nerve. 

The  paralytic  secretion  of  saliva. 

The  theory  of  secretion  suggested  by  the  facts  that  have 
been  advanced. 

DEMONSTRATIONS.    * 

Stimulation  of  the  chorda  tympani. 

Comparison  of  the  pressure  of  saliva  in  the  gland  duct  with 
that  of  the  blood  in  the  femoral  artery. 

The  action  of  atropin  and  of  pilocarpin  on  the  gland. 

9 


XIV.  THE  VARIETIES  AND  FUNCTIONS  OF  INGESTA. 

The  body  must  de])e]id  ni)()U  food  iiinttf'rs  for  the  mainten- 
ance of  its  structure  and  as  the  source  of  its  energy.  The 
nature  of  the  alimentary  substances  which  might  be  supposed 
most  readily  to  fulfill  these  functions. 

The  loss  of  energy  to  the  food  in  tlie  body. 

The  source  of  energy  of  plant  life. 

The  different  kinds  and  chemical  composition  of  the  sub- 
stances entering  into  foodstuffs:  proteids;  albuminoids;  fats; 
carbo-hydrates;  salts  and  water;  condiments,  etc. 

The  physical  and  chemical  characters,  and  chemical  reac- 
tions of  the  various  kinds  of  alimentary  substances. 

Proteids  form  the  oidy  class  of  of  foods  which  can  probably 
alone  maintain  life;  but  the  normal  diet  contains  all  the  diff'er- 
ent  kinds  of  food  matter. 

The  history  of  the  various  food  stuffs  in  the  body,  and  the 
form  under  which  they  appear  in  the  <'(jesfa. 

In  general  the  nitrogen  of  foods  reappears  in  the  crystalline 
bodies  of  the  excreta,  and  hydrocarbons  and  carbohydrates 
reappear  as  water  and  carbonic  acid. 

Liebig's  classification  of  foods  into  plasfic  and  respii'dinry. 

Objections  to  this  division. 

CLASSIFICATION  OF  INGESTA. 

f  Supply  material  for  the  forma- 
I  tion  and  restoration  of  tissues. 
Foods  ■{  Supply  the  energy  for  the 
I  construction  and  activity  of 
1^      the  body. 


Ingest a: 


Do  not  as  such  form  a  part  of 
the  living  tissues,  but  are  me- 
dia necessary  to  their  activity. 
A  second  class  of  them  acts 
Force  regulators  -|  as  a  collection  of  stimulating 
substances  which  produce 
effects  out  of  proportion  to 
the  amount  of  material  eni- 
l^      ployed. 


—72— 

Any  ingested  substance  is  not  restricted  in  its  function  to 
one  of  the  above  classes,  but  may  probably  at  the  same  time 
supply  energy  and  tissue  material  to  the  body,  and  serve  as  a 
force  regulator  to  the  activities  of  the  body. 

The  two  kinds  of  force  regulators  represented  by  a  saline 
solution  and  a  condiment. 

The  force  regulating  power  of  drugs. 

The  usefulness  of  cooking. 

DEMONSTRATIONS. 

The  chemical  reactions  of  proteids. 
The  chemical  reactions  of  fats. 

The  chemical  reactions  of  starch,  dextrin,  glycogen  and 
glucose. 


XV,    DIGESTION ;  AND  THE  ACTIVITIES  AND  STRUCTURE  OF 
THE  PARTS  INVOLVED  IN  IT, 

THE  STRUCTURE  AND  ARRANGEMENT  OF  THE 
MOUTH  PARTS. 

The  anatomy  of  the  buccal  cavity  and  parts  in  connection 
with  it.  The  siib-maxillary,  the  parotid  and  the  sub-lingual 
glands  and  their  openings. 

Structure  of  the  buccal  mucous  membrane. 

The  tongue;  its  muscles,  nerves  and  papill*. 
■  The  teeth ;  the  two  sets  of  permanent  and  milk  teeth ;  the 
number  in  each.     The  shape  and  parts  of  the  various  teeth. 
The  criista  petrosa;  dentine j  enamel. 

THE  PHYSIOLOGY  OF  SALIVA. 

Saliva  as  found  in  the  mouth  is  the  mixed  product  of  the 
three  pairs  of  salivary  glands,  of  the  glands  of  the  tongue 
and  adjacent  parts,  and  of  the  buccal  epithelium. 

The  physical  and  chemical  characters  of  saliva. 

The  solid  bodies  found  in  saliva;  the  food  detritus;  epithel- 
ium cells;  "salivary  corpuscles." 

The  function  of  saliva  in  assisting  deglutition. 

The  physiological  process  of  secretion  and  influences  mod- 
ifying it.  "Watering"  of  the  mouth;  the  "rice  ordeal." 
The  normal  reflex. 

Quantity  of  saliva  secreted. 

THE  DIASTATIC  ACTION^  OF  SALIVA. 

The  conversion  of  starch  into  sugar  under  the  action  of 
saliva.  The  greater  part  of  the  sugar  which  is  formed  is 
maltose. 


—74— 

The  influence  of.  temperature  on  the  rapidity  of  the  diasta- 
tic  action. 

Exposure  to  the  temperature  of  boiling  water  destroys  the 
diastatic  power  of  saliva.  The  action  is  arrested  in  a  medium 
containing  as  much  as  0.1  HCl  free,  and  strong  alkalis  destroy 
the  body  in  the  saliva  which  produces  the  change. 

The  amount  of  starch  which  may  be  changed  into  sugar 
bears  no  definite  relation  to  the  amount  of  saliva  employed. 
The  diastatic  power  of  the  saliva  does  not  seem  to  decrease 
proportionately  to  the  extent  of  the  change  which  it  brings 
about. 

The  diastatic  action  of  saliva  is  due  to  the  presence  in  it  of 
an  (uu'mal  ferment,  Ptrjdlin,  which  is  probably  an  organic  but 
non-proteid  product  of  the  activity  of  the  salivary  glands. 

The  diastatic  action  of  saliva  is  more  vigorous  in  a  neutral 
than  in  an  alkaline  solution.  The  effect  of  peptones  on  the 
activity  of  ptyalin. 

The  distinctive  characters  of  ferments.  Organized  and 
unorganized  ferments. 

The  special  characters  of  the  saliva  obtained  from  different 
glands. 

THE  PROCESS  OF  DEGLUTITION. 

The  masticated  mouthful  of  food  is  brought  together  in  a 
heap  upon  the  back  of  the  tongue,  and  thence,  by  a  compli- 
cated series  of  co-ordinated  movements,  is  transferred  to  the 
stomach. 

The  protective  movements  of  the  respiratory  apparatus,  and 
the  function  of  the  epiglottis. 

The  co-ordination  of  movement  in  the  mouth  parts  in  pho- 
nation,  deglutition,  etc. 

The  process  of  deglutition  may  be  divided  into  three  stages : 
(1)  Avhile  the  food  is  still  within  the  mouth,  the  movement  is 
purely  voluntary  and  may  be  slow  or  rapid.  ( 2 )  When  the 
food  reaches  the  common  buccal  and  respiratory  chamber  of 
the  pharynx,  the  movement  is  nearly  purely  reflex,  or  involun- 


tai'y,aiKl  is  then  most  i-apid.  (H)  "VVlieii  the  food  reaches  the 
uesophagns  its  Jiioveiuent  is  again  slower  and  quite  invohm- 
tary,  nnd  the  mouthful  is  carried  by  a  peristaltic  contraction 
to  the  stomach. 

The  nervous  mechanisms  involved  in  the  swallowing  move- 
ment.    The  centre  in  the  iitcduUd.. 

The  histological  structure  of  the  oesophagus. 

The  mechanisms  and  processes  im^olved  in  roiin'h'ii(/. 
The  stimulus  to  the  movement  may  be  either  peripheral  or 
central.     Majendie's  experiment.     Nausea. 

THE  STRUCTURE  AND  PHYSIOLOGY  OF  THE  STOMACH. 
THE  ANATOMY  AND  HISTOLOGY  OF  THE  STOMACH. 

The  shape,  anatomical  connections,  and  nervous  and  vascu- 
lar supply  of  the  stomach.     The  fundus. 

The  empty  stomach  is  always  contracted. 

The  three  coats  of  the  stomach:  (1)  muscular;  (2)  areolar; 
(3)  mucous. 

The  muscular  coat  is  composed  of  unstriated  tissue.  Its 
layers  of  longitudinal,  oblique  and  circular  fibres. 

The  cardiac  and  pyloric  sphincters.     The  pyloric  "valve." 

The  areolar  coat.     Division  of  blood-vessels  in  it. 

The  mucous  membrane.     The  rugm  and  their  cause. 

The  shape  and  cellular  elements  of  the  glands  of  the  mucous 
membrane.  The  difference  between  the  glands  of  the  pyloric 
and  other  regions  of  the  stomach.  The  blood  and  lymph  ves- 
sels of  the  mucous  membrane. 

The  nerve  cells  within  the  stomaqh  wall. 

THE  GASTRIC  JUICE  AND  ITS  SECRETION. 

The  fluid  obtained  from  the  stomach  of  a  dog  with  gastric 
fistula  by  means  of  electrical,  mechanical,  or  chemical  stimula- 
tion of  the  mucous  membrane.  Dilute  alkalis  readily  excite 
the  secretion. 

Flushing  of  the  mucous  membrane  during  digestion. 

The  quantity  of  gastric  juice  secreted  in  24  hours. 


—76- 
THE  CHEMISTRY  OF  THE  GxlSTRIC  JUICE. 

The  gastric  juice  of  the  dog  contains  about  0.45  p.  c.  solid 
matter,  of  which  half  is  inorganic  saline,  and  half  organic  mat- 
ter, the  ferment  pepsin,  mucus,  etc.  The  reaction  is  always 
acid,  due  to  the  presence  of  free  HCl.  Lactic  and  butyric 
acids,  which  are  frequently  present,  are  probably  due  to  fer- 
mentations of  the  food  matter,  and  not  to  the  secretory  activity 
of  the  stomach.  The  amount  of  free  HCl  is  about  0.2  p.  c.  of 
that  of  the  normal  juice. 

The  secretion  of  gastric  juice  is  not  continuous,  but  depends 
upon  stimulation  of  the  mucous  membrane.  The  relation  of 
absorption  from  the  stomach  to  the  amount  and  quality  of  the 
juice  secreted. 

The  variation  in  the  quantity  and  quality  of  the  gastric 
juice  at  different  stages  of  secretion. 

THE  DIGESTIVE  POWERS  OF  THE  GASTRIC  JUICE. 

The  proteolytic  digestive  powers  of  the  gastric  juice  are  due 
to  the  action  of  a  ferment  pepsin,  which  is  made  in  and  se- 
creted by  the  cells  of  the  stomach  glands.  Pepsin  is  probably 
an  organic  but  non-proteid  body. 

The  presence  of  free  acid  is  necessary  to  the  action  of  gas- 
tric juice.  The  power  of  the  juice  is  destroyed  by  the  temper- 
ature of  boiling  water.  The  rapidity  of  digestion  depends 
upon  the  temperature. 

On  starch  the  gastric  juice  has  no  effect,  though  it  may  set 
free  starch  grains  which  are  held  together  by  proteid  sub- 
stances. 

The  glands  of  the  stomach  appear  to  secrete  a  ferment  which 
changes  grape  sugar  to  maltose,  and  the  mucus  of  the  superfi- 
cial epithelium  contains  a  ferment  capable  of  changing  cane 
sugar  to  maltose.  An  excess  of  cane  sugar  in  the  food  causes 
an  increased  secretion  of  mucus. 

The  mechanical  function  of  the  mucus  as  a  cleanser  of  the 
alimentary  canal. 

On  fats  the  gastric  juice  has  no  effect,  though  they  are  set 


free  by  the  solution  of  the  proteid  and  gelatiniferous  i)ortion 
of  their  cell  envelopes. 

AlbiDuinoid  substances  are  dissolved  by  the  gastric  juice. 

Such  mineral  salts  as  are  soluble  in  dilute  acids  are  dis- 
solved by  gastric  juice. 

The  chief  digestive  power  of  the  gastric  juice  consists  in 
its  decomi)osition  of  proicids  by  which  they  are  converted 
into  soluble,  diffusible  substances  called  peptones. 

Experiments  upon  the  digestive  power  of  gastric  juice  may 
be  carried  out  either  with  natural  or  artificial  juice. 

Artificial  gastric  juice  may  be  prepared  by  extracting  the 
minced  mucous  membrane  of  the  stomach,  (1)  with  water, 
(2)  with  dilute  hydrochloric  acid  (0.2  p.  c. ),  (3)  with  glycer- 
in, (4)  or  with  glj^cerin  after  standing  under  strong  alcohol. 

Gastric  juice  acts  most  rapidly  at  about  the  body  tempera- 
ture, and  is  inert  at  0"C. 

The  presence  of  free  ac-id,  best  HCl  0.2  p.  c,  is  necessary 
to  the  activity  of  the  juice. 

The  acid  is  used  up  in  digestion  and  gradually  disappears 
from  an  artificial  solution. 

The  ferment,  pepsin,  does  not  appear  to  be  used  up  in 
digestion. 

Evidence  that  pepsin  is  formed  by  changes  in  the  stomach 
glands  after  death;  that  it  is  made  during  secretion  and  not 
stored  up  in  the  cells. 

The  pro-ferment,  pepsinogen. 

The  activity  of  the  gastric  juice  is  greatly  hindered  by  the 
accumulation  of  the  products  of  digestion. 

The.  histological  changes  which  the  gastric  gland  cells 
undergo  in  digestion. 

The  changes  as  to  granulation  u'hich  digestive  cells  in  gen- 
eral go  through  in  their  activity. 

The  functions  of  the  different  kinds  of  cells  of  the  stomach 
glands.  The  relation  of  the  glands  in  the  pyloric  part  of  the 
stomach  to  those  in  other  regions  of  the  organ. 

The  milk  ferment.     Rennet. 

10 


—78— 
The  gastric  juice  has  aiitiseptic  properties. 
THE  CHANGES  OF  PROTEIDS  IN  GASTRIC  DIGESTION. 

The  characteristic  swelling  of  the  proteid  substance  and  its 
gradual  solution. 

The  formation  of  soluble  albumin,  precipitable  by  boiling. 

The  formation  of  p<irapeptoiie  or  acid  albumin.  Dilute 
acid  alone  may  effect  these  changes. 

The  formation  of  pepfone.     Dyspcpione. 

Meissner's  A,  B,  and  C  peptones. 

Complete  and  incomplete  peptones. 

Characters  of  perfect  peptones:  peptones  are  soluble  in 
water,  but  are  not  precipitated  by  boiling;  they  answer  the 
chemical  tests  for  proteids;  they,  unlike  other  proteids,  are 
readily  diffusible.  They  are  not  precipitated  by  strong  acetic 
acid  and  potassium  f  errocyanide,  as  are  the  incomplete  pep- 
tones. 

Kiihne's  theory  of  the  division  of  proteid  substances  by 
gastric  digestion  into  two  groups — Hcmi-peptone  and  AnU- 
pepione. 

The  formation  of  peptones  appears  to  be  brought  about  by 
a  hydration  of  the  proteid. 

THE  HISTORY  OF   THE  FOOD  WITHIN   THE   MOUTH 
AND  STOMACH. 

The  effect  of  mastication  and  the  mechanical  and  chemical 
functions'of  saliva. 

The  swallowed  saliva  excites  the  flow  of  gastric  juice,  as 
does  probably  the  mere  emell  of  food. 

The  digestive  action  of  saliva  upon  starch  is  not  interfered 
with  by  the  acidity  of  the  gastric  juice  to  the  same  extent  as 
would  be  the  case  in  a  pure  acid  of  the  same  strength. 

The  mechailical  and  chemical  changes  of  the  food  in  the 
stomach.  The  usefulness  of  thorough  mastication.  The  me- 
chanical dissolution  of  the  fats,  starches,  and  proteids.  The 
nature  of  the  movement  of  food  in  the  stomach.     The  chyme. 


— 7i)- 

Tlie  processes  at  solution,  absorption,  ;ni(l  passage  into  the 
intestine. 

The  rapidity  of  digestion  in  the  stomach  and  intluences 
modifying  it:  nature  of  the  food;  method  of  cooking;  state  of 
division;  temperature;  rate  of  absorption;  the  efficiency  of  the 
gastric  juice  and  rapidity  of  its  secretion;  the  energy  of  move- 
ment which  mixes  the  food. 

THE    MECHANISMS    OF   SECKETIOxN    AND   OF    MOVE- 
MENT IN  THE  STOMACH. 

Tlie  only  nerves  reaching  the  stomach  are  branches  from 
the  vagi  and  the  splanchnics. 

Normal  gastric  juice  is  secreted  after  division  of  boths  sets 
of  nerves.  The  essential  secretory  mechanism  seems  to  be 
local.  The  food  is  brought  directly  into  contact  with  the 
secretory  membrane. 

The  influence  of  emotions  on  secretion. 

The  normal  mucous  membrane  is  flushed  during  digestion; 
it  becomes  pale  on  cutting  through  the  vagi,  and  reddens 
again  when  the  central  ends  of  these  nerves  are  stimulated. 

Afferent  vaso-motor  impulses  seem  to  travel  from  the 
stomach  along  the  vagi,  while  efferent  vaso-motor  impulses 
descend  to  the  stomach  in  the  splanchnic  fibres. 

The  natu.re  and  cause  of  the  movements  of  the  stomach. 

The  empty  stomach  is  contracted;  the  empty  intestine  is 
relaxed. 

The  influence  of  mechanical  distention  on  the  movement  of 
the  stomach. 

The  influence  of  extrinsic  nerves  upon  movement  and  secre- 
tioii. 

Vomiting. 

THE  CHANGES  WHICH  THE  Ft)OD  UNDERGOES  IN 
THE  INTESTINE,  AND  THE  DIGESTIVE  ORGANS 
INVOLVED  IN  THEM. 

The  digestive  fluids  which  are  poured  into  the  intestine  are 
all  alkaline  in  reaction  and  come  from  three  sources:     (1) 


—80— 

the  Pancreas,  pancreaiic  juice;  (2)    the  Intestinal  Mucous 
Membrane  snccus  entericus;  the  Liver,  bile. 

THE  AI^ATOMY  A^D  HISTOLOGY  OF  THE  PANCREAS. 

The  relative  position  of  the  openings  of  the  bile  and  pan- 
creatic ducts  into  the  intestine  in  man  and  in  other  animals. 

The  lobulated  structure  of  the  gland. 

The  histological  appearance  of  the  pancreas.  The  ducts; 
the  single  acini;  the  gland  cells,  their  outer  hyaline  and  inner 
granular  zone. 

The  phases  of  histological  change  which  the  gland  cells 
undergo  in  digestion.  The  observation  of  the  pancreas  in  a 
living  rabbit. 

In  general,  the  granular  matter  of  a  resting  secretory  cell 
is  distributed  throughout  the  whole  of  the  cell;  while  as  a 
result  of  activity,  the  granules  are  fewer  in  number  and  are 
accumulated  round  the  lumen  of  the  gland  on  the  inner  border 
of  the  cells. 

The  difficulty  of  establishing  a  permanent  pancreatic  fistula. 
■The  pancreatic  juice  begins  to  flow  from  a  fistula  immedi- 
ately on  food  being  taken;  the  rate  of  secretion  increases  till 
about  the  fourth  hour,  then  decreases  for  an  hour,  and  then 
increases  again,  reaching  a  second  maximum  at  the  eighth 
hour  after  taking  food,  afterward  declining. 

The  amount  of  pancreatic  juice  secreted  in  24  hours. 

THE  CHARACTEES  AND  POWERS  OF  PANCREATIC  JUICE. 

Normal  pancreatic  juice  is  a  clear,  viscid  fluid,  frothing 
when  shaken.     It  has  a  decided  alkaline  reaction. 

The  fluid  contains  about  8  p.  c.  solids,  consisting  of  albumin, 
alkali  albumin,  leucin  and  tyrosin,  some  fats  and  soaps,  and  a 
considerable  amount  of  soda  carbonate.  The  presence  of 
leucin,  tyrosin,  and  soaps  is  probably  due  to  digestive  changes 
in  the  juice  after  its  secretion. 

The  pancreatic  juice  is  probably  the  most  important  of  all 
the  digestive  fluids.  It  probably  normally  contains  several 
distinct  kinds  of  ferment. 


—81  — 

The  action  of  the  pancreatic  juice  upon  i^larch  is  similar  to 
that  of  saliva,  but  is  apparently  more  powerful. 

Neutral  f<(U  are  emulsified  by  pancreatic  jviice,  and  ai-e 
partly  decomposed  into  glycerine  and  a  fatty  acid. 

Unlike  the  gastric  juice,  pancreatic  juice  does  not  dissolve 
gelatiniferous  substances. 

On  profciih,  pancreatic  juice  exercises  a  powerful  solvent 
action,  converting  them  into  pepfories. 

The  digestion  of  proteids  does  not  cease  at  this  stage,  but 
peptones  are  farther  decomposed  into  two  nitrogenous  crys- 
talline bodies,  leucin  and  fijrosiii. 

The  complicated  changes  undergone  by  proteids  in  their 
digestion;  the  by-products  formed  are  alkali-albuminates  in- 
stead of  acid-albuminates  as  in  the  case  of  gastric  digestion. 

The  special  proteid  ferment  of  the  pancreatic  juice  is  called 
trypsin. 

Kuhne's  theory  of  the  changes  undergone  by  j^roteids  in 
gastric  and  pancreatic  digestions. 

The  digestion  of  proteids  by  natural  or  artificial  pancreatic 
juice  in  an  alkaline  medium  is  attended  with  the  formation  of 
indol,  a  substance  having  an  offensive  feecal  odor. 

Indol  is  not  formed  when  the  digestion  is  carried  on  in  the 
presence  of  salicylic  acid.  It  is  probably  not  a  product  of 
digestion,  but  of  the  activity  of  adventitious  organized  fer- 
ments. 

A  proteid,  as  fibrin,  undergoing  pancreatic  digestion,  appears 
to  be  gradually  corroded  and  crumbled;  it  does  not  swell  as 
when  acted  on  by  the  gastric  juice. 

If  the  pancreatic  ferments  be  exposed  to  the  temperature  of 
boiling  water  their  digestive  power  is  destroyed. 

An  artificial  extract  of  the  pancreas  may  be  made  which 
shall  have  all  the  powers  of  the  natural  juice. 

The  extract  of  the  perfectly  fresh  gland  has  little  or  no  di- 
gestive power. 

The  fully  formed  ferment  does  not  exist  stored  up  in  the 
gland  cells  during  life.  The  living  cells  do  not  contain  ti-t/psiit, 
but  hold  an  antecedent  to  this  ferment,  called  zij)tto(jeii. 


—82— 

Trypsin  is  quickly  formed  in  the  excised  pancreas  when 
this  is  exposed  to  a  warm  temperature. 

Addition  of  strong  acetic  acid  rapidly  converts  zymogen 
into  trypsin,  and  a  powerful  digestive  fluid  can  then  be  made  by 
extracting  the  gland  with  a  1  p.  c.  solution  of  soda  carbonate. 

THE  RELATION  OF  THE  PROTEID  FERMENTS  OF  THE  GAS- 
TRIC AND  PANCREATIC  JUICES. 

Gastric  juice  can  digest  only  in  an  acid  medium.  Pancre- 
atic juice  digests  best  in  an  alkaline  fluid,  1  to  2  p.  c.  soda  car- 
bonate, but  is  still  active  in  a  neutral  or  slightly  acid  solution. 

When  pepsin  and  the  pancreatic  ferments  are  mixed  to- 
gether in  an  acid  solution,  pepsin  acts  upon  and  destroys  the 
trypsin. 

THE   STRUCTURE   OF  THE   INTESTINE  AND  THE  SE- 
CRETION PRODUCED  BY  ITS  GLANDS. 
ANATOMY  AND  HISTOLOGY  OF  THE  INTESTINE. 

The  arbitrary  division  of  the  small  intestine  into  (hiodenum, 
jcjuniiui  and  ileum. 

The  three  coats;  )ii.u,sciilar,  areolar,  and  mucous.  The  circu- 
lar and  longitudinal  muscle  fibres. 

The  nerve  plexuses  of  Auerbach  and  of  Meissner. 

The  'valvuke  couia'venfes. 

The  r//// of  the  small  intestine;  their  capillary  and  lymph 
vessels;  the  layer  of  muscle  cells;  the  striated  borders  of  the 
covering  epithelium. 

The  glands  of  Brunner. 

The  "crypts"  of  Lieberkiihn. 

Peyer's  "patches." 

The  secretion  of  the  intestinal  glands,  the  Succus  Eiifericus, 

is  an  alkaline  fluid  having  slight  proteolytic  and  amylolytic 

digestive  powers. 

THE  BILE. 

The  bile  is  the  secretion  of  the  liver  cells,  and  in  the  inter- 
vals between  digestive  activity  is  stored  up  in  the  gall  bladder. 


—83— 
CHEMICAL  AND  PHYSICAL  CHARACTERS  OF  BILE. 

The  bile  is  decidedly  alkaline  in  reaction. 

The  green  bile  of  herbivora  and  the  yellow  bile  of  carniv- 
ora. 

The  biliary  pigments  hilivcrdiii  and  hilirithin. 

The  clay  color  of  the  fseces  when  bile  is  prevented  from 
entering  the  intestine. 

Pettenkofer's  test  for  bile  acids. 

The  bile  salts;  fniirocholafc  and  fiJycocholafc  of  .soda. 

Gmelin's  test  for  bile  pigments. 

THE  PROCESS  OF  SECRETION  AND  THE  DIGESTIVE  FUNC- 
TION OF  BILE. 

The  secretion  of  the  l)ile  increases  rapidly  after  taking 
food  and  reaches  its  maximum  in  4  to  10  hours  after  a  meal. 
The  bile,  unlike  the  saliva,  is  secreted  under  a  pressure  much 
less  than  that  of  the  blood. 

The  passage  of  dilute  acid,  as  of  the  contents  of  the  stom- 
ach, over  the  intestinal  orifice  of  the  bile  duct,  causes  a  gush 
of  bile  into  the  intestine  occasioned  by  contraction  of  the 
muscles  of  the  gall  bladder.     This  action  is  purely  reflex. 

If  bile,  or  a  solution  of  bile  salts,  be  added  to  a  fluid  con- 
taining the  products  of  gastric  digestion,  the  complete  and 
incomplete  peptones  in  solution  are  precipitated.  Most  of 
the  pepsin  is  carried  down  mechanically  by  the  precipitate- 
Excess  of  bile  redissolves  the  precipitate  and  the  resulting 
solution  is  alkaline  in  reaction. 

The  precipitation  of  the  dissolved  gastric  peptones  prevents 
their  too  rapid  progress  along  the  intestine,  and  removes  the 
pepsin  whose  action  is  destructive  to  trypsin. 

Bile  has  a  slight  emulsifying  power  over  fats,  which  is  much 
increased  when  mixed  with  pancreatic  juice. 

Bile  possesses  some  antiseptic  power. 

It  probably  mechanically  assists  in  the  absorption  of.  fats, 
as  these  pass  more  readily  through  membranes  moistened 
with  bile. 


— §4— 

Bile  may  furnish  alkali  for  the  formation  of  soaps  in  diges- 
tion. 
Bile  interferes  with  the  process  of  gastric  digestion. 
The  amount  of  bile  secreted  in  24  hours. 
The  effect  of  withdrawing  bile  from  the  body. 
The  history  of  the  food  in  the  small  intestine.     The  chyle. 

ABSORPTION  FROM  THE  SMALL  INTESTINE. 

The  diffusion  of  liquids.     The  absorption  of  fats. 

The  pumping  action  of  the  villi  which  assists  absorj)tion. 

The  diffusion  of  water  through  the  wall  of  the  small  intes- 
tine is  about  equal  in  both  directions,  for  the  contents  of  the 
ileum  are  as  fluid  as  those  of  the  duodenum.  The  action  of 
purges. 

The  mucous  membrane  of  the  large  intestine  is  crowded 
with  tubular  glands,  but  supports  no  villi. 

The  contents  of  the  large  intestine  rapidly  lose  water  and 
become  dry.  They  become  acid  in  reaction  from  the  products 
of  intrinsic  fermentation.  The  caecal  digestion  of  herbivor- 
ous animals. 

The  gases  found  in  the  large  intestine: — CO2,  N,  CH4,  H, 
SH. 

The  chemistry  of  the  fseces. 

The   function   of  mucus  as  a  cleanser   of  the  alimentary 

THE  MOVEMENTS  OF  THE  INTESTINE. 

Fibres  from  the  vagi  and  splanchnics  unite  the  intestine 
with  the  brain. 

The  peristaltic  contraction  of  the  excised  intestine. 

The  normal  movements  of  the  intestine  and  their  stimulus. 

DEMONSTRATIONS. 

The  conversion  of  starch  into  sugar  by  saliva;  influence  of 
temperature. 

The  effect  upon  its  amylolytic  power  of  boiling  saliva. 
The  reaction  and  digestive  power  of  natural  gastric  juice. 


Digestion  of  proteids  with  artificial  gastric  juice.  The  in- 
fluence of  the  state  of  division  of  the  jn-oteid;  the  acidity  of 
the  juice;  the  temperatm*e. 

Effect  of  boiling  the  juice. 

Products  and  by-products  formed  during  proteid  digestion. 

The  characters,  solubility  and  diffusibility  of  perf 3ct  pep- 
tones. 

Pancreatic  digestion ;  of  fats ;  of  starch ;  of  proteids.  The 
formation  of  leucin  and  tyrosin.     The  formation  of  iinloJ. 

Pancreatic  digestion  without  formation  of  indol. 

Bile;  the  acid  test  of  Pettenkofer. 

Gmelin's  test  for  bile  pigments. 

The  precipitation  and  resolution  by  bile  of  gastric  peptones. 

The  emulsion  of  oil  in  bile  and  pancreatic  juice. 

The  peristaltic  movement  of  the  intestines. 

The  demonstration  of  the  lacteals  after  their  natural  injec- 
tion with  chyle. 


XVI,   THE  PHYSI(JL(][;Y  OF  NUTRITION. 

The  subject  of  nntriti  oji  is  a  chemical  study,  aud  it  has  to 
do  with  the  chinges  which  mitters  entering  the  living  b.jdy 
undergo  tiiere. 

The  waste  matters  of  the  body  are  at  a  lower  chemica 
potential  than  the  foad  matters,  and  it  is  believed  that  this 
energy  difference  is  exactly  represented  by  the  vital  force  oj 
the  animal. 

The  food  matter  absorbed  into  the  body  does  not  necessarily 
fall  directly  to  the  chemical  standpoint  of  the  wastes,  but  it 
probably  most  often  reaches  the  condition  of  the  latter  after 
passing  through  a  series  of  synthetic  as  well  as  analytic 
changes. 

The  products  of  digestion  must  be  worked  over  by  living 
tissues  before  they  form  part  of  the  normal  blood. 

THE  STRUCTURE  OF  THE  LIVER. 

The  liver  is  the  chief  seat  of  changes  undergone  by  tli9 
digested  food  in  its  preparation  for  the  tissues.  The  blood 
coming  from  this  organ  is  probabl)^  the  warmest  in  the  body. 
In  the  embryo  the  liver  is  proportionately  large,  and  is  there 
probably  the  seat  of  the  formation  of  blood-corpuscles.  In 
many  lower  animals  the  liver  secretes  digestive  juices;  among 
mammals  its  only  secretion,  and  that  is  partly  an  excretion,  is 
bile. 

Most  of  the  blood  of  the  liver  is  collected  from  the  viscera 
into  its  pf>rtal  circulation,  from  which  the  circulation  in  the 
hepatic  arteries  and  capillaries  is  distinct. 

The  division  of  the  liver  substance  into  lobules. 

Glisson's  capsule  and  the  three  interlobular  vessels,  the  he- 
patic artery,  the  portal  vein  and  the  bile  duct,  inclosed  by  it. 
The  intra-lobular,  the  sub-lobular  and  the  hepatic  veins. 


—88— 

The  hepatic  cells;  granular  polyhedral  bodies  often  contain- 
ing globules  of  fat  and  masses  of  glycogen. 

The  histological  changes  of  the  hepatic  cells  during  diges_ 
tion. 

The  origin  of  the  bile  ducts  between  the  liver  cells. 

CONSTRUCTIVE  METABOLISM  OF  THE  BODY. 

THE  PART  PLAYED  BY  THE  LIVER  IK  THE  HISTORY  OF 

GLYCOGEN. 

The  liver  is  preeminently  the  organ  of  those  chemical 
changes  in  the  body  which  do  not  involve  the  formation  or 
disintegration  of  permanent  tissues. 

Glycogen  may  be  found  in  considerable  quantity  in  the 
liver  cells  of  normal  animals;  it  may  also  be  extracted  in  small 
amounts  from  probably  any  living  tissue. 

When  food  is  withheld  from  an  animal  the  quantity  of  gly- 
cogen in  its  liver  begins  immediately  to  diminish,  and  finally 
probably  completely  disappears. 

If  food  be  again  given,  the  accumulation  of  glycogen  in  the 
liver  proceeds  rapidly  till  it  has  reached  its  former  amount. 
Carbohydrate  foods  are  particularly  favorable  to  the  laying  up 
of  glycogen  by  the  liver. 

The  glycogen  is  no  doubt  constructed  by  the  activity  of  the 
liver  cells  out  of  the  food  matter  coming  from  the  digestive 
tract. 

When  the  liver  is  removed  from  the  body  and  allowed  to  lie 
in  a  warm  place,  after  a  time  it  is  found  that  the  glycogen  has 
disappeared  and  that  sugar  has  been  produced  in  its  place.  If 
the  liver  be  boiled  while  quite  fresh,  it  is  found  to  contain 
much  glycogen  but  little  or  no  sugar.  When  the  liver  is  re- 
moved from  the  body  its  store  of  glycogen  is  turned  into  sugar 
by  the  action  of  a  ferment,  probably  produced  within  the  liver 
cells. 

It  is  probable  that  the  glycogenetic  function  of  the  liver 
consists  in  the  storage  within  the  liver  cells  of  the  carbohy- 
drate moieties  of  the  food  matter  in  the  comparatively  insolu- 


—89- 

ble  form  of  glycogen.  Under  normal  conditions  this  glycogen 
is  transformed  into  soluble  sugar  at  a  certain  definite  rate,  tlie 
sugar  passing  into  the  general  circulation  for  the  supply  of 
the  tissues.  Through  this  function  of  the  liver,  both  tlie 
overloading  of  the  tissues  with  carbohydrate  matter  at  the 
time  of  feeding  and  their  suffering  for  want  of  it  in  time  of 
hunger,  are  prevented. 

DIABETES. 

Temporary  diabetes  may  be  artificially  j)roduced  in  an 
animal.  If  a  well-fed  rabbit  be  punctured  in  the  vaso-motor 
region  of  the  medulla  the  flow  of  the  urine  will  be  increased 
and  in  one  to  two  hours  it  will  contain  considerable  sugar, 
which  after  a  day  or  two  will  have  disappeared  again.  If  the 
animal  be  previously  starved  so  that  the  liver  contains  little 
or  no  glycogen,  the  ui-ine  after  the  operation  will  contain 
little  or  no  sugar.  The  sugar  found,  then,  has  come  from 
stored-uj)  glycogen. 

The  obscurity  of  the  cause  of  this  diabetes. 

Mild  and  severe  forms  of  natui'al  diabetes  and  the  relation 
of  the  nature  of  the  food-supply  to  them. 

FORMATION  OE  FAT  IX  THE  BODY. 

The  fluctuation  in  the  quantity  of  fat  in  the  body. 

Histological  changes  in  the  connective  tissue  corpuscle 
which  is  being  converted  into  a  fat  cell. 

Fatty  degeneration  of  proteid  containing  tissues. 

The  ripening  of  cheese. 

The  fat  of  the  body  may  be  produced  from  the  metabolism 
of  food  matters  other  than  fat.  A  greater  quantity  of  fat 
may  appear  in  the  milk  of  a  cow  than  was  contained  in  the 
food  of  the  animal.  The  amount  of  wax  produced  by  bees 
far  exceeds  that  of  the  fat  found  in  the  saccharine  food  of 
the  creatures.  It  has  l)een  shown,  in  one  instance,  that  for 
every  100  i)arts  of  fat  in  the  food  of  a  fattening  pig,  472  parts 
were  laid  up  as  fat  in  the  body. 

Proteid  foods  as  a  source  of  fat. 


—90— 

The  fat  of  the  living  body  consists  of  certain  average  pro- 
portions of  tri-olein,  tri-palmitin  and  tri-stearin,  which  are 
unaltered  by  the  variation  of  the  proportions  of  those  sub- 
stances in  the  food;  therefore  the  fat  of  the  body  is  not  sim- 
ply that  of  the  food  stored  up  unchanged. 

The  chemical  changes  by  means  of  which  carbohydrates 
and  proteids  may  give  rise  to  fats, 

THE   STRUCTURE    AND    SECRETIOlSr   OF   THE    MAMMARY 

GLANDS. 

Each  human  mammary  gland  is  comj)osed  of  a  number  of 
distinct  lobes  which  are  bound  together  by  connective  tissue 
containing  much  fat.  Each  lobe  is  farther  divided  into 
smaller  and  smaller  lobules.  The  ductules  of  neighboring 
acini  unite,  and  the  ducts,  from  15  to  20  in  number,  of  the 
various  lobes  thus  formed  open  separately  upon  the  nipple. 
The  ducts  are  dilated  near  their  external  openings  so  as  to 
form  small  milk  reservoirs.  The  ducts  and  the  terminal 
acini  are  lined  by  short  columnar  epithelium. 

Fresh  milk  is  alkaline  in  reaction  but  may  become  acid 
while  yet  in  the  gland  duct.  Its  chemical  constituents  are, — 
water;  casein,  serum  albumin;  fats;  milk  sugar;  potassium 
phosphate,  calcium  phosphate,  potassium  chloride,  magnesium 
phosphate. 

The  fatty  globules  forming  the  emulsion  are  surrounded  by 
albuminous  envelopes. 

Colosh'iiDi  differs  from  ordinary  milk  in  being  deficient  in 
casein  and  proportionately  rich  in  albumin. 

Milk  sugar  is  readily  changed  by  fermentation  into  lactic 
acid,  which  then  causes  coagulation  of  the  casein. 

The  protoplasm  of  the  mammary  gland  cell  probably  forms 
all  the  organic  constituents  of  the  milk. 

Histological  changes  in  the  gland  cells  during  lactation. 

The  fats  of  milk  are  increased  by  proteid  feeding  and  the 
amount  of  milk  sugar  is  not  dependent  on  the  carbohydrates 
eaten. 


— ill— 

The  ferment  secreted  1)y  the  stomach  glands  -wliich  coagu- 
lates casein. 

THE  STRUCTURK  AND  PHYSIOLOGY  OF  THIC  SPLEEN. 

The  structure  of  the  spleen  is  much  like  that  of  a  lym- 
phatic gland.  The  organ  consists  of  a  reticular  framework 
of  bands  of  (>lastic  tissue,  in  the  interspaces  of  which  rests 
the  red-brown  spleen  pulp  which  consists  of  a  network  of 
branched  connectiA^e  tissue  corpuscles,  through  the  interstices 
of  which  oozes  blood  in  which  are  for  nd  red  corpuscles  appar- 
ently undergoing  destructive  metamorphosis.  The  trabecular 
substance  of  the  spleen  contains  much  plain  muscular  tissue. 
The  outer  connective  tissue  coat  of  the  smaller  arteries  is 
frequently  dilated  into  small  spheroidal  bodies  which  have 
the  structure  of  lymph  follicles,  the  so-called  MaJj)i(j/tiaii  cor- 
puscles. 

The  spleen  may  be  extirpated  without  danger  to  the  life  of 
the  animal.  After  such  an  operation  there  seems  to  be  an 
increase  in  the  size  of  the  lymphatic  glands  and  in  the  activity 
of  the  medulla  of  bones. 

The  spleen  increases  in  size  up  to  about  the  fifth  hour  of 
digestion,  and  then  diminishes  again. 

The  amount  of  blood  passing  through  the  spleen  is  proba- 
bly regulated  by  the  action  of  the  muscle  fibres  found  in  the 
trabecular  tissue  of  the  organ.  Rhythmic  contractions  of  the 
spleen. 

The  spleen  is  probably  a  seat  of  the  formation  of  white  cor- 
puscles and  destruction  of  red  corpuscles  of  the  blood.  The 
peculiar  "spleen  corpuscles"  which  contain  fragments  of  red 
blood  disks. 

The  pulp  of  the  spleen  is  very  rich  in  so-called  extractive 
matters. 

THE  ORIGIN  OF  UREA. 

The  living  tissues  are  continually  being  wasted  and  restored, 
and  the  nitrogen  of  the  wastes  is  nearly  all  contained  in  the 
urea  excreted. 


—92— 

Muscular  tissue  contains  kreatin,  uric  acid  and  other  crys- 
talline nitrogenous  bodies,  but  no  urea. 

THE  EELATIOI^  OF  THE  KIDJS^EYS   TO   THE   EOEMATIOI^ 

OF  UREA. 

It  is  probable  that  the  nitrogenous  crystalline  substances 
of  the  muscle  are  waste  products  of  the  tissue  and  in  part 
antecedents  of  urea. 

There  is  some  reason  to  believe  that  the  cells  of  the  renal 
tubules  may  effect  the  conversion  into  urea  of  certain  antece- 
dents of  the  latter  which  are  found  in  the  blood. 

THE  RELATION  OF  PAI^CREATIC  DIGESTION  AND  OF  THE 
LIVER  TO  THE  FORMATIOJT  OF  UREA. 

The  pancreatic  digestion  of  proteids  may  give  rise  in  the 
intestine  to  considerable  amounts  of  leucin  and  tyrosin. 
Leucin  injected  into  the  alimentary  canal  reappears  as  urea 
in  the  urine.  The  liver  always  contains  urea  in  its  substance. 
It  is  not  improbable  that  the  liver  cells  turn  into  urea  the 
leucin  produced  by  excessive  proteid  digestion  in  the  intestine. 

The  possible  chemical  process  by  which  the  liver  forms 
urea  from  leucin,  as  indicated  by  the  results  which  follow  the 
ingestion  of  sarcosin. 

Increase  of  proteid  in  the  food  increases  the  amount  of 
urea  excreted.  It  is  probable  that  the  amount  of  leucin  and 
tyrosin  formed  in  pancreatic  digestion  is  proportional  to  the 
excess  of  proteid  in  the  food. 

Uric  acid,  though  less  oxidized  than  urea,  is  probably  not 
an  antecedent  of  the  latter.  Uric  acid  replaces  the  urea  in 
the  excrement  of  birds. 

The  chemical  functions  of  the  liver  which  are  indicated  in 
the  elimination  of  hippuric  acid. 

STATISTICAL  STUDY  OF  NUTRITION. 

The  proportion  in  which  the  various  tissues  exist  in  the 
body.  The  relative  diminution  of  the  tissues  during  starva- 
tion. 


-93— 

The  history  o£  nitrogen  excretion  in  the  urine  of  a  starving 
animal.     Lnxvfi  consumpi ion. 

The  study  of  the  changes  taking  place  in  the  body  by  a 
comparison  of  the  substances  entering  it  with  those  coming 
out  of  it. 

The  effect  of  nitrogenous  foods  on  the  chemical  [)r()cesses 
of  the  body.     Niivogcn  equiUhrinin. 

The  Banting  system  of  dietetics. 

The  effects  of  fatty,  of  carbohydrate  food,  and  of  gelatine. 

The  functions  of  these  foods  as  force  regulators. 

The  effects  of  salts  in  the  food. 

It  is  probable  that  the  urea  excreted  has  at  least  two  differ- 
ent sources;  arising  in  pretty  definite  quantities  from  the 
nitr(^genous  tissues,  and  also  coming  in  fluctuating  quantities 
from  the  decomposition  of  proteid  matter  which  never  forms 
part  of  the  general  tissues. 

The  dietetic  value  of  the  various  food  stuffs. 

THE  NATURE  OF  THE  PROCESSES  WHICH  GIVE  RISE 
TO  THE  BODILY  ENERGY. 

The  amount  of  energy  evolved  by  the  body  is  represented 
by  the  difference  between  the  chemical  potentials  of  the  food 
and  the  waste  matter,  and  is  wholly  unaffected  by  the  manner 
in  which  this  degradation  is  brought  about. 

In  every  change  of  matter  in  the  body  by  which  molecules 
are  made  more  unstable,  energy  is  absorbed;  in  every  change 
in  which  the  reverse  takes  place,  energy  is  evolved. 

The  energy  set  free  in  the  body  all  reappears  either  as  heat 
or  mechanical  energy. 

Those  movements  of  the  body  which  involve  friction  are 
attended  with  a  loss  of  heat.  The  difference  between  the 
mechanical  energy  of  the  blood  in  the  aorta  and  in  the  ven;e 
cavrP  must  be  represented  by  an  equivalent  of  heat,  produced 
by  friction  in  the  blood-vessels.  The  heat  lost  by  radiation, 
conduction  and  evaporation  owes  its  origin  to  chemical 
changes  in  the  body. 

12 


^94— 
tpie  energy  supply  of  the  Body. 

The  amount  of  energy  stored  up  in  tlie  various  food  matters 
may  be  determined  in  heat  units  when  tliey  are  completely 
burned. 

The  direct  oxidation  of  the  following.  Gives  rise  to 

dried  at  100°  Centigrade:  Gram,  degree,        Met.-Kilo. 

1  gram  Beef-fat 9069  3841 

1  gram  Arrowroot 3912  1657 

1  gram  Beef-muscle  purified  with  ether.  ,       5103  2161 

1  gram  Urea 2206  934 

Supposing  that  all  the  nitrogen  of  proteid  food  goes  out  as 
urea,  1  gram  of  dry  proteid,  such  as  dried  beef-muscle,  would 
give  rise  to  about  one-third  gram  of  urea,  hence : 

Gram,  degree,  Met.-Kilo. 

1  gram  Proteid 5103  2161 

Less 
I3  gram  Urea 735  331 

Available  energy  of  1  gram  of  Proteid. .  4368  1850 

(Foster's  Physiology.) 

'      THE  SOUllCE  OF  ENERGY  OF  MUSCULAR  WORK. 

It  was  the  belief  of  Liebig  that  the  non-nitiogenous,  or 
"respiratory,"  foods  were  oxidized  in  the  body  to  maintain  its 
temperature,  while  the  nitrogenous,  or  "plastic,"  foods  went 
to  form  the  living  tissues,  and  that  the  functional  changes  of 
the  latter  gave  rise  to  the  nitrogen  of  the  egesta. 

It  is  probable  that  muscular  labor  does  not  involve  the 
destruction  of  the  nitrogenous  part  of  the  muscle  molecule. 
The  amount  of  nitrogen  excreted  is  not  increased  by  muscular 
work. 

The  experiments  of  Parkes,  of  Fick  and  Wislicenus.  The 
experiments  of  Flint. 

The  amount  of  carbonic  acid  excreted  is  immediately  and 
greatly  increased  by  muscular  work. 

The  experiments  of  Pettenkof er  and  Voit  comparing  the 
oxidations  of  the  body  while  in  a  state  of  rest  and  at  work. 


—95— 

Tho  oxidations  of  tlic  l)o(ly  o(;cur  in  the  tissiK^s  and  not  in 
tlui  l)loo(l  or  the.  liinj^s.  These,  oxidations  firi^  not  immediately 
dependent  upon  the  respiration.  Excess  ol;  carbonic  acid  given 
off  during  tlie  day  and  of  oxygen  absorbed  in  the  nigiit. 

The  muscle  molecule  ])robfd)ly  consists  of  an  essential 
nitrogenous  ]X)rtion  capable  of  adding  to  itself  certain  com- 
bustible non-nitrogenous  matters,  which  latter,  during  func- 
tional activity,  are  oxidized  and  give  rise  to  free  energy. 

ANIMAL  HICAT. 

The  energy  diiference  between  the  food  and  waste  matters 
all  reappears  as  heat  in  a  resting  animal.  During  work,  the 
oxidations  of  the  body  and  the  heat  produced  are  increased. 

The  muscles,  glands  and  central  nervous  tissues  are  the 
chief  seats  of  heat  prodviction  in  the  body. 

The  mechanical  energy  of  the  circulating  blood  finally 
reappears  as  heat. 

The  body  temperature  of  different  animals.  Cold-blooded 
and  warm-blooded  animals.  The  temperature  of  hibernating 
animals. 

I'he  difference  between  the  temperatures  of  different  i^arts 
of  the  body  and  the  variation  of  temperature  in  the  same 
part. 

The  blood  coming  fr6m  the  liver  is  the  Avarmest  in  the 
body. 

The  blood  as  a  heat  distributer. 

THE   MAINTENANCE    OF    A    CONSTANT   BODY  TEMPER- 

xiTURE. 

THE   REGULATION   OF   THE   LOSS   OK   HEAT. 

The  loss  of  heat  through  various  channels  is  calculated  as 
follows : 

In  warming  I'seces  and  urine 2.5  p.  c. 

In  warming  expired  air 5.2  p.  c 

In  evaporating  the  water  of  respiration.  14.7  p.  c. 
In  conduction,  radiation  and  evaporation 

by  the  sl\in 77.5  p.  c. 


—96— 

The  means  by  wliicli  the  loss  of  heat  through  the  lungs  and 
skin  is  controlled. 

The  reflex  excitement  of  the  organs  through  which  heat  is 
lost  to  the  body.     Temperature  nerves. 

The  perfection  of  this  regulation  as  shown  by  the  high 
temperatures  which  can  be  borne  in  a  dry  atmosphere. 

In  some  hair-covered  animals  the  chief  loss  of  heat  is  by 
means  of  the  lungs  and  mouth. 

The  function  of  the  non-conducting  layer  of  subcutaneous 

fat. 

THE  REGULATION  OF  HEAT  PRODUCTION. 

The  oxidations  in  the  body  of  a  warm-blooded  animal  are 
increased  by  a  low  surrounding  temperature;  those  of  a  cold- 
blooded animal  are  decreased. 

This  increased  production  of  heat  in  warm-blooded  animals 
is  probably  the  result  of  a  reflex  action  in  which  the  activity 
of  a  thermogenic  nerve-centre  is  involved.  A  curarized  ani- 
mal, or  one  whose  spinal  cord  has  been  divided,  shows,  like  a 
cold-blooded  creature,  diminished  oxidations  when  the  sur- 
rounding temperature  is  lowered. 

The  action  of  the  thermogenic  centre  increases  the  chemi- 
cal changes  of  the  tissues,  leading  to  an  excessive  absorption 
of  oxygen  and  evolution  of  carbonic  acid. 

It  has  been  made  certain  that  the  loss  of  heat  from  the 
body  is  under  nervous  control,  chiefly  through  means  of,  1, 
the  vaso-motor  centres;  2,  the  sweat  centres;  3,  the  respira- 
tory centres. 

It  has  been  made  highly  probable  that  the  production  of 
heat  is  under  the  nervous  control  of  centres  which  cause,  1, 
an  increase  of  heat  production;  2,  a  diminution  of  heat  pro- 
duction. That  is,  there  are  probably  heat  producing  and 
heat  inhibitory  nerve-centres. 

THE  INFLUENCE  OF  THE  NERVOUS  SYSTEM  ON  THE 
NUTRITIVE  PROCESSES  OF  THE  BODY. 

Many  obscure  facts  point  to  a  nervous  regulation  of  the 
nutritive  processes  of  the  body,  but  in  no  instance  has  such 


—97— 

an  action  been  proven.  Inflammation  of  the  cornea  which 
follows  section  of  the  trigeminal  nerve.  Pneumonia  which 
succeeds  division  of  the  vagi. 

It  is  at  present  safest  to  consider  that  the  liefilthy  nutrition 
of  a  part  depends  upon  the  Hn)ii  total  of  its  physiological 
actions  rather  than  on  the  influence  exerted  by  a  special 
"  trophic  "  nerve. 

DEMONSTRATION. 

Extraction  of  glycogen  from  the  fresh  liver,  and  the  con- 
version, by  the  liver  ferment,  of  glycogen  into  sugar. 


XVII.  THE  SPINAL  CORD. 

STRUCTURE  OF  THE  SPINAL  CORD  AND  ACCESSOIJV 

PARTS. 

The  spinal  C(H'd  is  closely  invested  by  the  vascular  y>/Vf  iiififn; 
which  gives  rise  to  the  connective  tissue  frame-work  of  the 
cord. 

Outside  the  pin  iiiafcr  is  the  (irddnioid  membrane,  and 
between  the  two  sheets  of  tissue  is  foimd  the  cereV)ro-spinal 
Huid. 

The  functions  of  the  cerebro-spinal  fluid. 

Surrounding  the  parts  just  described  is  a  dense  membrane, 
the  diird  vinfci-,  which  is,  at  points,  attached  to  the  wall  of  the 
neural  canal. 

The  spinal  cord  is  held  in  position  by  the  spinal  nerves 
entering  it,  and  by  ligaments  passing  fn mi  the  ^jk^  wo/^t  to 
the  (hu-a  Dudo-. 

The  cervical  and  lumbar  enlargements  of  the  cord. 

The  caiida  equiiui  and  the  fihim  iermimde. 

Each  spinal  nerve  divides  into  two  branches,  the  anterior 
and  jDosterior  spinal  roots,  just  after  entering  the  neural  canal. 
All  the  sensory  fibres  of  the  spinal  nerves  enter  the  cord  by 
the  posterior  roots;  all  the  motor  fibres  leave  the  cord  by  the 
((.idei'ior  roots.  Each  posterior  root  bears  a  ganglion  near  the 
point  of  its  juncture  with  the  anterior  root. 

The  function  of  the  ganglion  of  the  posterior  nerve-root. 

The  spinal  cord  is  divided  longitudinally  on  its  anteritn- 
side  by  a  broad  shallow  groove,  the  diderioi-  tncdian  fissure. 
Posteriorly  the  cord  is  similarly  divided  by  a  deeper  and  nar- 
rower posterior  median  fissure,  which  is  filled  by  a  sheet  of 
infiected  connective  tissue.  The  two  sets  of  spinal  nerve- 
roots  enter  the  cord  along  tolerably  definite  lines,  the  Udend 


—100— 

fissures.  As  marked  out  by  these  fissures,  the  cord  may  be 
considered  to  be  made  up  of  a  pair  of  anferioi;  a  pair  of  laf- 
eral,  and  a  pair  of  posterior-  cohimns.  The  posterior  columns 
have  further  indicated  on  their  surface  a  narrow  posterior 
median  cohimn. 

The  central  canal  of  the  spinal  cord,  lined  by  cuboidal  cil- 
iated epithelium. 

Running  through  the  cord  is  a  core  of  gray  matter  which 
has  a  double  crescent  shape  in  cross-section. 

The  nervous  matter  of  the  white  substance  of  the  cord  is 
composed  of  meduUated  nerve  fibres ;  that  of  the  gray  sub- 
stance is  made  of  nerve  cells  and  nerve  fibres  chiefly  without 
the  fatty  sheath. 

The  variation  in  form  and  mass  of  the  gray  matter  in  dif- 
ferent parts  of  the  cord.  The  gelatinous  substance  in  the  pos- 
terior cornua. 

The  shape  and  distribution  of  the  nerve  cells  and  the  con- 
nection of  nerves  with  them. 

The  anterior  white  commissure  and  the  gray  commissures. 

Most,  if  not  all,  the  nerve  fibres  reaching  the  spinal  cord, 
sooner  or  later  enter  its  gray  substance. 

The  nervous  elements  of  the  cord  are  intimately  bound  and 
supported  by  a  connective  tissue  frame-work.  The  neuroglia. 

THE  SPINAL  CORD  AS  A  CENTRE  FOR  REFLEX 
ACTIONS. 

The  spinal  cord  contains  nervous  centres  capable  of  send- 
ing out  nervous  discharges  which  may  stir  up  complicated, 
co-ordinated,  and  adaptive  movements. 

These  movements  are  never  initiated  in  the  cord,  but  are 
brought  about  by  impulses  reaching  the  cord  from  without ; 
that  is,  they  are  not  spontaneous,  but  reflex  in  character. 

The  stimulation  of  the  terminal  organs  of  the  afferent 
nerves  is  much  better  adapted  for  arousing  reflexes  than  the 
direct  stimulation  of  a  nerve  trunk. 

The  nerve  cell  requires  time  to  cause  an  efferent  nervous 


clischiirgo  after  having  received  an  impulse  from  an  afferent 
nerve.  The  retlex  nerve  cell  is  readily  excited  to  action  by  a 
succession  of  distinct  impulses  reaching  it,  l)ut  rarely  by  a 
single  one. 

Extremely  feeble  stimuli  when  summated  in  the  s[)inal 
cord  may  produce  powerful  effects.     Examples. 

The  inhibition  of  a  reflex  action  may  be  occasioned  by  the 
strong  stimulation  of  any  afferent  nerve,  or  by  the  influence 
of  nerve  centres  in  the  brain  or  spinal  cord  other  than  the 
reflex  centre. 

The  physiological  nature  of  "shock." 

The  spinal  cord  has  no  power  of  leariiitifj  to  adapt  its  activ- 
ities to  new  conditions. 

In  a  certain  sense  the  spinal  cord  may  be  looked  on  as  a 
servant  of  the  centres  of  intelligence  which  has  learned,  under 
their  instruction,  to  carry  out  alone  certain  oft  repeated 
actions. 

There  is  no  evidence  of  the  spinal  cord  possessing  a  con- 
scious intelligence. 

THE  SPINAL  CORD  AS  A  COLLECTION  OF  AUTOMATIC 

CENTRES. 

One  of  the  functions  of  the  spinal  cord,  probably,  is  to  act 
nearly  independently  by  means  of  special  centres  whose  duty  it 
is  to  preserve  the  organic  welfare  of  the  body,  and  whose 
powers  in  part  are,  no  doubt,  automatic.  The  nervous  control 
of  the  sijhincter  muscles  of  the  body;  the  sexual  centres; 
muscular  tonicity;  subsidiary  vaso-motor  centres. 

The  peculiar  movements  of  a  mammal  with  divided  spinal 
cord. 

THE  PATHS  OF  CONDUCTION  IN  THE  SPINAL  CORD. 

AVe  usually  have  conscious  sensation  of  the  impulses  reach- 
ing the  spinal  cord;  in  such  cases  the  impulses  must  be  trans- 
mitted to  the  brain. 


—102— 

We  cannot  suppose  that  all  the  nerve  fibres  entering  tli6 
cord  are  individually  represented  by  fibres  passing  to  the  brain 
in  that  organ,  for  the  number  of  nerve  fibres  in  the  spinal 
cord  is  not  great  enough  to  admit  of  this.  In  such  a  case, 
also,  the  shape  of  the  spinal  cord  would  be  that  of  an  inverted 
cone. 

We  may  suppose  that  the  fibres,  or  most  of  them,  from  the 
periphery  on  the  one  hand,  and  from  the  brain  on  the  other, 
are  connected  with  certain  nerve  centres  in  the  gray  matter  of 
the  spinal  cord  by  whose  mediation  impulses  reaching  the 
cord  from  many  different  sources  may  be  sent  out  of  it  by  a 
single  channel,  or  conversely.  In  this  sense  the  nerve  centres 
of  the  cord  act  as  relay  stations  for  the  transmission  of  im- 
pulses reaching  them  from  any  quarter. 

The  segmental  distribution  of  the  gray  matter  in  the  cord. 
The  area  of  gray  matter  in  a  cross  section  of  the  cord  rises 
and  falls  with  the  sectional  area  of  the  nerve  fibres  entering 
the  cord  at  that  level. 

It  has  been  attempted  to  determine  the  anatomical  and 
physiological  grouping  of  the  nerve  fibres  of  the  spinal  cord, 

(1)  by  a  study  of  the  direction  in  which  cut  fibres  degenerate; 

(2)  by  the  different  periods  at  which  various  collections  of 
the  fibres  assume  the  medullary  sheath;  (3)  by  pathological 
data;  (4)  by  observation  of  the  results  following  physiologi- 
cal experiment. 

All  impulses,  whether  sensory  or  motor,  passing  between 
the  brain  and  the  body  at  large,  cross  the  middle  line  and  end 
in  the  side  opposite  to  that  in  which  they  originated. 

The  decussation  occurs  at  the  level  of,  and  below  the  pons 
varolii. 

Sensory  impulses  probably  cross  to  the  opposite  side  lower 
down  in  the  spinal  cord  than  do  the  volitional  impulses. 

Volitional  impulses  cross  most  largely  in  the  medulla  and 
travel  along  the  cord  in  the  lateral  and  anterior  columns,  and 
enter  the  nervous  centres  of  the  anterior  cornua  of  the  gray 
matter  of  the  cord,  whence  they  emerge  in  the  anterior  spinal 


—  lo;-;— 

roots.  Volitional  fil)res  which  have  not  already  crossed  to 
the  opposite  side  in  the  medulla  prol)al)ly  i)ass  down  the  cord 
in  the  anterior  column  on  the  same  side  as  that  on  which  they 
originate,  nntil  they  cross  the  middle  line  and  then  enter  the 
lateral  column  of  the  opposite  side. 

Sensory  impulses  reaching  the  cord  enter  the  ])()sterior  cor- 
nua  of  its  gray  matter  or  its  posterior  white  columns,  and 
soon  crossing,  })roceed  to  the  brain  chieily  in  the  lateral  col- 
umns. 

Tracts  of  degeneration  in  the  spinal  cord  accom[)anying 
various  forms  of  paralysis. 

The  most  marked  i-esults  of  lateral  hemi-section  of  the 
spinal  cord  is  a  paralysis  of  voluntary  motion  and  hyperes- 
thesia on  the  same  side  below  the  injury,  Avith  a  loss  of  sen- 
sation on  the  opposite  sitle;  ]jrobal)ly  neither  of  these  effects 
is  complete. 

The  functions,  sensory  and  motor,  wliich  are  abolished  by 
a  hemi-section  of  the  cord  may  be  gradually  recovered  with- 
out reunion  of  the  divided  parts. 

Purely  tactual  and  painful  sensory  impulses  probably  pass 
through  the  cord  along  different  paths.  The  phenomena  of 
analgesia. 

The  gray  matter  of  the  cord  can  no  doubt  conduct  in  any 
direction  the  impulses  which  reach  it. 

DEMONSTRATIONS. 

Comparison  of  the  retiex  action  obtained  by  stimulating 
the  skin  and  a  nerve  trunk  of  a  beheaded  frog. 

The  purposeful  character  of  retiex  actions. 

The  summation  of  stimuli  in  the  spinal  cord. 

The  inhibition  of  refle:?  action  in  a  frog,  (a)  through  the 
strong  stimulation  of  an  afferent  nerve;  ("ft^through  stimula^ 
tion  of  the  optic  lobes, 


XYIIl.  THE  BRAIN. 

THE  MEDULLA  OBLONGATA. 

The  inednlla  l)esides  being  the  pathway  of  the  nerve  fibres 
connecting  the  brain  and  spinal  cord,  contains  a  number  of 
automatic  and  reflex  nerve  centres  which  especially  preside 
over  the  "organic  "  functions  of  the  body.  Among  the  nerve 
centres  are  included, — a  respiratory  centre ;  a  cardio-inhibitory 
centre ;  a  diabetic  centre ;  a  vaso-motor  centre ;  centre  of  deglu- 
tition; centre  of  reflex  secretion  of  saliva;  a  vomiting  centre; 
centre  of  movements  for  oesophagus  and  stomach;  and  prob- 
ably centres  for  the  co-ordination  of  movements  of  the  body. 

The  medullary  centres,  though  capable  of  independent 
action,  are  no  doubt  normally  under  the  influence  of  other 
similar  centres  in  higher  parts  of  the  brain. 

THE   CHANGES   PRODUCED  IN  AN  ANIMAL  BY  THE 
REMOVAL  OF  ITS  CEREBRUM. 

A  frog  or  a  pigeon  bears  well  the  extirpation  of  the  cere- 
brum, but  a  mammal  sooner  or  later  succumbs  to  such  an 
operation. 

The  loss  of  the  cerebrum  involves  the  loss  of  spontaneous 
movement;  an  animal  without  that  organ  stirs  only  in  answer 
to  a  stimulus. 

With  the  loss  of  its  cerebrum  an  animal  appears  to  lose  its 
faculty  of  iiercepiion  and  the  power  of  iormingjiHlgmenis 
The  deterioration  of  the  animal  is  in  its  psychical  powers. 

The  aspects  of  a  frog  and  of  a  pigeon  after  removal  of  the 
cerebral  lobes  are  nearly  normal.  Food  is  not  voluntarily 
taken,  tlunigh  it  is  swallowed  when  placed  in  the  mouth. 
No  sign  of  fear  can  be  aroused.  The  animal  exhi))its  no  fur- 
ther evidence  of  the  possession  of  free  will. 


—106— 

The  most  complex  co-ordinated  movements  may  still  be 
carried  out.  The  balancing  and  swimming  of  a  frog,  and  the 
flight  of  a  pigeon  whose  cerebral  hemispheres  have  been  re- 
moved. Such  an  animal  appears  to  retain  its  normal  sensa- 
tions. A  frog  deprived  of  its  cerebrum  avoids  obstacles  in 
leaping. 

The  same  general  results  follow  the  destruction  of  the  cere- 
brum in  a  mammal.  A  rabbit  or  a  rat  so  treated  ceases  to 
notice  food.  Its  gaze  is  attracted  by  a  moving  light,  and  it 
may  utter  plaintive  cries  and  leap  on  being  stimulated.  Its 
sensations  are  preserved  but  its  perceptions  are  lost. 

THE  LOCALIZATION  OF  FUNCTION  IN  THE 
CEREBRUM. 

THE  STRUCTURE  OF  THE  CEREBRUM. 

The  interior  of  the  cerebral  hemispheres  is  chiefly  com- 
posed of  masses  of  nerve  fibres  which  terminate  in  the  cortex. 
The  nerve  cells  of  the  cerebrum  are  contained  in  the  cortical 
substance,  a  thin  sheet  of  gray  matter  which  overlies  the  con- 
voluted surface  of  the  hemispheres. 

In  general  the  cerebrum  may  be  considered  to  be  the  seat 
of  thought,  of  conciousness,  and  of  will  power. 

It  is  not  certain  whether  the  manifold  functions  of  the  cere- 
bral cortex  are  separately  localized  in  the  various  convolutions, 
or  whether  the  whole  brain  is  to  be  regarded  as  a  complicated 
machine  in  which  the  activity  of  one  part  involves  that  of  all 
the  rest. 

The  effect  of  gradual  removal  of  a  pigeon's  brain  is  a 
gradual  loss  of  psychical  power  in  the  animal. 

In  certain  pathological  conditions,  as  in  the  disease  aphasia, 
there  is  strong  suggestion  of  a  localization  of  function  in  the 
cortex. 

The  limited^anastomosis  of  the  blood-vessels  of  the  cortex  is 
suggestive  of  localization. 

There  may  be  produced  in  an  animal  definite  movements  or 
signs  of  sensation,  as  a  result  of  the  electrical  stimulation  of 


—107— 

well  defined  areas  of  the  cerebral  convolutions.  Mechanical  or 
chemical  stimulation  of  the  cortex  is  not  followed  by  positive 
results. 

The  different  results  following^  stimulation  of  the  coi'tex  in 
the  various  stages  of  mori)hia  narcosis. 

Removal  of  a  "motor"  area  of  the  cortex  is  said  by  some  to 
be  followed  by  a  loss  of  \'oluiita)-y  control  over  the  muscles  for- 
merly excited  by  the  stimulation  of  that  area.  Removal  of  a 
"sensory"  area  is  said  in  like  manner  to  involve  a  loss  of  the 
appropriate  sensations. 

The  results  supporting  the  theory  of  localization,  as  ob- 
tained in  the  exi)eriments  of  Fritsch  and  Hitzig,  of  Ferrier  and 
of  Munk. 

The  nature  of  the  i)henomena  l)r()ught  out  by  artificial 
stimulation  of  the  cortex,  and  of  those  which  follow  the  extir- 
pation of  various  areas. 

There  is  a  gradual  recovery  from  the  motor  paralysis  or 
loss  of  sensation  which  follows  removal  of  a  limited  area  of  the 
cortex. 

In  this  recovery  the  function  of  the  lost  part  has  not  been 
assumed  by  any  definite  homologous  area  in  another  part  of 
the  brain. 

Extensive  lesions  of  the  brain  have  been  suffered  by  men 
without  permanent  motor  or  sensory  disturbance. 

According  to  the  experiments  of  Goltz,  there  is  no  distinct 
localization  of  function  in  the  cerebral  cortex;  but  a  gradual 
loss  of  psychical  power,  of  sensation,  and  of  definite  volun- 
tary motion,  follows  extirpation  of  an}'  part  of  the  cerebral 
convolutions  in  the  dog,  and  these  disturbances  are  more  ex- 
tensive and  less  readily  recovered  from,  the  more  widespread 
the  lesion. 

After  suffering  such  an  operation  an  animal  responds  in  a 
reflex  manner  to  stimuli  much  more  readily  than  usual. 

Exaggeration  of  the  "  tendon  reflex  "  in  motor  paralysis. 

Parts  of  the  brain  below  the  cerebrum  are  no  doubt  capalile 
of  carrying  out  independently  complicated  activities  in  which 
simple  sensations  are  involved. 


—108— 

The  difference  between  psyclioses  and  neuroses. 
Cerebral  "  reaction  time." 

THE  CORPORA  STRIATA  AND  THE  OPTIC  THALAMI. 

The  so-called  "basal  ganglia  "  are  masses  of  gray  tissue  con- 
taining many  nerve  cells.  Most  of  tlie  fibres  of  the  crura 
cerebri  pass  into  the  basal  ganglia  before  proceeding  to  the 
cortex  of  the  brain.  The  anterior  fibres  of  the  peduncles  enter 
the  corpora  striata,  and  the  posterior  fibres  join  the  optic  thai- 
ami,  before  continuing  into  the  cerebral  substance.  The  nerve 
fibres  which  enter  the  basal  ganglia  are  no  doubt  largely  con- 
nected with  nerve  cells  found  there. 

When  a  lesion  involves  both  the  corpus  striatum  and  optic 
thalamus  of  one  side,  there  is  loss  of  voluntary  motion  and  of 
sensation  on  the  opposite  side  of  the  body,  without  necessary 
impairment  of  intellectual  faculties. 

It  is  probable  that  the  basal  ganglia  act  as  sets  of  relay  sta- 
tions which  mediate  between  the  cerebral  cortex  and  nervous 
centres  in  lower  parts  of  the  brain  and  spinal  cord. 

There  is  some  reason  to  believe  that  the  corpora  striata  are 
chiefly  concerned  in  the  modification  of  volitional  impulses 
passing  to  it  from  the  cerebral  convolutions;  and  that  the  optic 
thalami  receive  the  sensory  impulses  before  they  proceed  to 
the  surface  of  the  brain. 

Injury  to  the  optic  thalami  is  followed  by  blindness  or  im- 
perfection of  vision. 

THE  CORPORA  QUADRIGEMINA. 

These  bodies  correspond  to  the  corpora  bigemina,  or  optic 
lobes,  of  the  frog  and  pigeon. 

The  nervous  centres  for  the  co-ordination  of  the  movement 
of  the  eyeballs  with  the  contraction  of  the  pupils  lie  in  or 
below  the  anterior  half  of  the  corpora  quadrigemina. 

The  manner  in  which  the  actions  of  these  centres  are  asso- 
ciated; when  the  visual  axes  are  converged  the  pupils  contract, 
when  the  axes  becomes  parallel  the  pupils  dilate. 


—109— 

Movements  of  the  opposite  eye  are  brought  about  by  the 
stimulation  of  the  corpora  t[uadrigemina  on  one  side. 

Extiri)ation  of  the  corpora  quadrigemina,  or  of  the  optic 
lobes,  on  one  side  produces  blindness  in  the  opposite  eye. 

The  seat  of  visual  sensations  appears  to  be  in  the  corpora 
quaih'igemina,  but  visual  perceptions  are  lost  when  the  cere- 
bral cortex  is  destroyed. 

Other  physiological  functions,  as  that  of  respiration,  prob- 
ably are  regulated  by  special  centres  situated  in  the  corpora 
quadrigemina. 

THE  CEREBELLUM. 

The  structure  of  the  cerebellum  and  the  manner  of  its 
association  with  the  rest  of  the  brain. 

The  chief  function  of  the  cerebellum  is  to  serve  as  a  col- 
lection of  nerve  centres  whose  action  maintains  the  equilib- 
rium of  the  body  and  co-ordinates  its  movements. 

Lesions  of  the  cerebellum  artificially  produced  are  followed 
by  unsteadiness  of  gait,  and  when  a  large  amount  of  nervous 
substance  is  lo3t  complete  failure  of  co-ordination  is  the  re  suit. 

Lateral  lesions  produce  more  effect  than  those  established 
in  the  median  line. 

Extensive  asymmetrical  injury  of  the  cerebellum,  as  of  sec- 
tion of  the  middle  peduncle  on  one  side,  produces  remarkable 
forced  movements  of  the  animal,  together  with  a  peculiar  roll- 
ing back  and  forth  of  the  eyes. 

Section  of  one  of  the  crura  cerebri  is  also  follow^ed  by 
forced  movements,  as  also  are  injuries  of  the  corpora  striata 
and  optic  thalami,  or  even  of  the  cerebral  cortex  alone. 

The  passage  of  a  galvanic  current  through  the  back  part 
of  the  head  produces  a  sensation  of  giddiness  and  a  rolling 
motion  of  the  eyes. 

There  is  no  reason  to  believe  that  the  cerebellum  is  con- 
nected with  the  sexual  functions.  The  special  sexual  centres 
appear  to  be  situated  in  the  lumbar  region  of  the  spinal  cord. 

14 


— no— 

The  cerebellum  is  probably  capable  of  learning  to  carry 
out  reilexly  new  and  complicated  purposive  actions. 

The  functions  of  the  infant's  brain. 

General  consideration  of  the  relation  of  the  activities  of 
the  various  parts  of  the  central  nervous  system. 

THE  SEMI-CmCULAR  CANALS  AND  THEIR  RELATION 
TO  THE  MAINTENANCE  OF  THE  EQUILIBRIUM 
OF  THE  BODY. 

THE  STEUCTURE  OF  THE  SEMI-CIRCULAR  CA^TALS. 

The  planes  of  the  three  membranous  canals  lie  approxi- 
mately in  the  three  dimensions  of  space. 

The  ampullar  enlargement  of  each  canal  and  the  modified 
termination  o£  the  filaments  of  the  auditory  nerve  within  it. 

The  cavity  of  each  canal  communicates  with  that  of  the 
utricle. 

The  whole  membranous  labyrinth  is  filled  with  endolympli. 

THE  EFFECT  OF  CUTTING  THE  SEMI-CIECULAR  CANALS 
IN  A  PIGEON. 

When  one  of  the  semi-circular  canals  of  a  pigeon  is  divid- 
ed, remarkable  disturbances  of  equilibrium  immediately  fol- 
low. When  one  of  the  horizontal  canals  is  cut,  the  head 
moves  from  side  to  side;  when  one  of  the  vertical  canals  is 
operated  on,  the  movement  is  up  and  down.  These  disturb- 
ances of  equilibrium  become  more  marked  when  a  number  of 
canals  is  divided,  and  the  animal  places  its  head  in  unusual 
positions  with  respect  to  the  body.  Gradual  recovery  takes 
place  if  but  one  or  two  canals  be  injured. 

Injury  of  the  semi-circular  canals  of  the  mammal  is  fol- 
lowed by  the  same  general  results  as  in  the  case  of  the 
pigeon. 

These  results  are  not  due  to  partial  muscular  paralysis,  nor 
probp,bly  to  unusual  auditory  sensations. 


— 1 1 1  — 

THE  SENb;:  OF  EQUILIBRIUM. 

The  maintenance  of  the  equilibrium  of  the  body  requires 

the   co-ordinated   activity    of     comi)licated    nerve-muscular 

mechanisms.     The   afPerent  impulses   which    determine    the 

action  of   this  motor  apparatus   may   arrive   from   differei.'j 

sources. 

The  body  must  know  its  })ositioii  in  reference  to  surround- 
ing objects  in  order  to  maintain  its  equilibrium.  Such  a 
knowledge  of  the  body's  position  may  be  attained  through 
visual  sensations,  facfilc  sensations,  and  ui iiscular  fiensations, 

But  it  has  been  shown  that  a  person  may  be  conscious  of  a 
change  of  position  without  the  excitement  of  any  of  the  fore- 
going sensations.  The  impulses  which  bring  this  information 
are  supposed  by  some  to  arise  in  the  sepai-circular  canals.  It 
is  possible  that  movements  of  the  body  may  cause  a  change 
of  jjressure  of  the  endolymph  within  the  semi-circular  canals 
upon  the  nervous  mechanisms  there,  the  intensity  of  excite- 
ment in  each  ampulla  depending  upon  the  direction  of  the 
movement.     The  truth  of  this  hypothesis  is  not  established. 

The  various  means  by  which  vertigo  may  be  produced. 

THE  CRURA  CEREBRI  AND  PONS  VAROLII. 

These  bodies  contain  considerable  gray  matter,  but  the 
chief  functions  we  can  ascribe  to  them  are  those  in  which  they 
serve  as  connecting  links  between  different  parts  of  the  central 
nervous  system.  Marked  disturbance  of  equilibrium  follows 
injury  of  either  the  crura  cerebri  or  the  pons  varolii. 

THE  BLOOD  SUPPLY  OF  THE  BRAIN. 

The  amount  of  blood  supplied  to  the  brain  is,  in  proportion 
to  the  size  of  the  organ,  probably  small. 

AVhen  the  brain  is  exposed  it  is  found  to  undergo  rhythmic 
alterations  of  volume,  occasioned  by  the  heart  beats  and  re- 
spiratory movements. 

During  its  periods  of  activity  the  brain  appears  to  receive 
more  blood  than  when  at  rest. 


—112— 

Owing  to  the  rigid  cranial  envelope  sudden  variations  of  the 
amount  of  blood  in  the  brain  subject  its  substance  to  such 
changes  of  pressure  as  may  affect  the  consciousness. 

The  blood  supply  of  the  brain  is  no  doubt  under  elaborate 
vaso-motor  regulation. 

DEMONSTEATIONS. 

The  phenomena  exhibited  by  a  pigeon  and  by  a  frog  after 
removal  of  the  cerebral  hemispheres. 

The  phenomena  of  "forced  movements." 

The  effects  following'^section  of  the  semi-circular  canals  in 
the  pigeon  and  the  frog.  <, 


XIX.  THE  EYE  AND  SIGHT. 

The  anatomical  mechanis^m  whose  excitement  gives  rise  to 
a  simple  sensation  consists  of  ( 1 )  a  peripheral  "  sense  organ,' 
( 2 )  an  afferent  nerve,  ( 3 )  a  central  nerve-cell  organ. 

It  is  only  the  activity  of  the  central  organ  which  directly 
affects  consciousness.  It  is  often  difficnlt  to  determine  in 
which  part  of  the  sense  apparatus  the  disturbance  which  gives 
rise  to  a  sensation  originates. 

The  difference  between  physical  and  physiological  "light." 
The  sensitiAJ^eness  of  the  retina  to  certain  ether  vibrations. 

Specific  nerve  energy. 

The  difference  between  simple  sensations  and  judgments. 

THE  STRUCTURE  OF  THE  EYE  AND  PARTS  NEAR  IT. 

The  small  third  eyelid  which  represents  the  nictitating 
membrane  of  som^  animals. 

The  perforated  lachrymal  papillse.  The  lachrymal  gland. 
The  Meibomian  glands. 

The  action  of  the  accessory  glandular  and  muscular  mechan- 
isms of  the  eye. 

The  reflex  secretions  from  the  lachrymal  glands,  and  the 
aid  rendered  by  winking  movements  to  the  emptying  of  the 
lachrymal  canals. 

The  six  muscles  for  the  movement  of  the  eyeball. 

The  eyeball.  The  oblique  entrance  of  the  optic  nerve.  The 
sclerotic  coat  and  cornea  continuous  with  it.  The  radius  of 
cui'vature  of  the  cornea  is  smaller  than  that  of  the  remaining 
sui'face  of  the  ej^eball.  The  choroid  coat;  its  blood-vessels, 
pigment-cells,  and  ciliary  processes.  The  iris;  its  inner  cii*- 
cular  and  outer  radial  plain  muscle  fibres;  its  vessels,  nerves 
and  pigment.     The  ciliary  muscles.     The  crystcdline  lens;  its 


—114— 

suspmsoi-fj  1i(/(nnenl.  The  sheet  of  tissue  known  as  the  "sus- 
pensory ligament"  is  attached  at  its  inner  edge  to  the  anterior 
surface  of  the  lens,  and  at  its  outer  edge  to  the  inner  surface 
of  the  ciliary  processes.  The  vitreous  humour  and  hyaloid 
membrane.  The  aqueous  humour.  The  anterior  and  2^os- 
terior  chambers  of  the  aqueous  humour.  The  ca/nal  of 
Schlemm.  The  retina;  the  ora  serrata;  the  macula  lutea 
and  fovea  centralis;  the  blood-vessels  of  the  optic  nerve  and 
their  distribution  in  the  retina. 

Commencing  at  its  anterior  surface  there  may  be  recognized 
in  the  1mm  an  retina  ten  distinct  layers;  (l)Membrana  liml- 
tans  interna;  (2)  layer  of  nerve  fibres;  (3)  layer  of  nerve 
cells;  (4)  inner  molecular  layer;  (5)  inner  nuclear  layer;  (6) 
outer  molecular  layer;  (7)  outer  nuclear  layer;  (8)  membrana 
limitans  externa;  (9)  layer  of  rods  and  cones;  (10)  layer  of 
tessellated,  pigment-holding  cells. 

The  macula  lutea,  or  yellow  spot,  is  free  from  blood-vessels 
except  at  its  margin.  The  blood-vessels  of  the  retina  ramify 
in  the  nerve  fibre  layer,  and  their  capillaries  do  not  extend 
outward  beyond  the  inner  nuclear  layer. 

The  fovea  centralis  contains  only  the  retinal  cones,  the  rods 
being  there  absent. 

The  optical  advantages  accruing  to  the  fovea  centralis  as 
the  spot  of  distinct  vision  from  the  absence  of  blood-vessels, 
and  of  the  inner  retinal  layers  in  it. 

The  pigment-free  part  of  the  choroid  which  forms  the 
tapetum  in  some  animals. 

THE  EYE  AS  AN  OPTICAL  INSTRUMENT. 

When  a  ray  of  light  falls  on  the  retina  we  become  conscious 
of  a  sensation  of  light. 

In  order  that  we  may  become  aware  of  the  form  of  a  dis- 
tant object,  an  image  of  it  must  be  thrown  upon  the  retina. 

The  laws  determining  the  formation  of  images  in  an  ordin- 
ary camera.     The  camera  obscura. 

The  eye  is  a  camera  made  up  of  a  dark  chamber  to  which 


—115— 

the  liglit  is  admitted  through  a  diai)hragra,  the  iris;  tAVo 
refracting  media,  tiie  cornea  and  crystalline  lens,  intercept  the 
light  before  its  entrance  into  the  retinal  chamber. 

The  refracting  power  of  a  lens  depends  (a)  upon  the  cur- 
vature of  its  surface,  (/>)  upon  the  refracting  power  of  its 
substance. 

The  foci  of  all  the  refracting  media  of  the  eye  fall  up(jn  an 
02)tic  axis  which  meets  the  retina  a  little  above  and  inside  of 
the  fovea  centralis. 

We  may  calculate  the  path  of  all  oblique  rays  entering  the 
eye  by  assuming  that  they  meet  the  optical  axis  at  a  "nodal" 
point  and  leave  the  axis  in  a  direction  parallel  to  the  first 
from  a  second  nodal  point.  The  nodal  j)oiuts  are  near 
together  on  the  optical  axis  within  the  lens.  Primary  and 
secondary  optical  axes. 

The  refraction  of  a  ray  of  light  entering  the  eye  occurs 
chiefly  at  the  anterior  surface  of  the  cornea  and  at  the  anterior 
and  posterior  surfaces  of  the  lens. 

The  inversion  of  the  retinal  image. 

The  spatial  projection  of  retinal  impressions. 

When  the  head  is  plunged  under  water  the  refraction  by 
the  cornea  is  nearly  done  away  with;  hence  the  marked  com- 
pensatory curvature  of  the  fish's  lens. 

The  anterior  and  posterior  surfaces  of  the  cornea  being 
.  nearly  parallel,  they  may  be  regarded  as  one. 

The  refractive  powers  of  the  aqueous  and  vitreous  humours 
are  nearly  the  same  as  that  of  the  cornea,  we  may  regard  the 
refracting  surfaces  of  the  lens  as  three,  the  anterior  surface 
of  the  cornea,  the  anterior  and  posterior  surfaces  of  the  lens. 

It  is  calculated  that  the  focus  of  the  refracting  media  of 
the  eye  lies,  for  parallel  rays,  14647  mm.  behind  the  poster- 
ior surface  of  the  lens  and  22.647  mm.  behind  the  anterior 
surface  of  the  cornea. 

The  reason  why  the  pupil  of  an  observed  eye  appears  dark. 
Albinos.     Principle  of  the  ojythahnoscope. 

The  luminous  eyes  of  some  nocturnal  animals. 


—US- 
ACCOMMODATION. 

The  focal  distance  at  which  a  distinct  image  of  an  object 
may  be  formed  by  light  passing  through  a  refracting  surface, 
the  refractive  index  remaining  the  same,  depends,  (a)  upon 
the  curvature  of  the  surface,  (6)  on  the  angle  which  the 
entering  rays  form  with  it.  In  order  that  an  image  which  is 
thrown  upon  a  certain  fixed  plane  may  remain  distinct  when 
one  of  those  factors  is  changed,  the  other  factor  must  under- 
go a  compensatory  change. 

If  this  accommodation  is  not  brought  about,  the  image  is 
replaced  by  a  series  of  blurred  "diffusion  circles." 

Accommodation  in  the  human  eye  as  illustrated  by  "  Schei- 
ner's  experiment."     The  near  limit  of  distinct  vision. 

In  the  normal  or  emmefropic  eye,  the  near  limit  is  at  a  dis- 
tance of  ten  to  twelve  centimetres;  the  far  limit  may  be 
regarded  as  at  an  infinite  distance.  In  the  short  sighted  or 
myopic  eye  the  near  liiiiit  is  brought  within  five  to  six  centi- 
metres distance  of  the  cornea  and  the  far  limit  at  a  variable 
but  not  considerable  distance.  In  the  far  sighted  or  hyper- 
metropic eye,  the  near  limit  of  distinct  vision  is  some  dis- 
tance away,  and  a  far  limit  does  not  exist.  In  the  three  cases, 
an  image  formed  by  rays  parallel  to  the  optical  axis  falls 
respectively  on  the  retina,  before  it  and  behind  it.  The  pres- 
byopic eyes  of  old  people. 

The  structural  or  physiological  peculiarities  which  occasion- 
these  various  defects. 

THE  APPARATUS  OF  ACCOMMODATIOK 

While  at  rest,  the  eye  is  accommodated  for  objects  at  an 
extreme  distance. 

In  accommodating  for  near  objects  two  movements  may  be 
observed  in  the  eye,  (1)  a  narrowing  of  the  pupil,  (2)  a 
change  in  the  curvature  of  the  anterior  surface  of  the  lens 
by  which  it  becomes  more  convex. 

In  its  normal  condition  the  lens  is  an  elastic  body  whose 
curved  surfaces  are  somewhat  flattened  by  the  pressure  of  the 


—117 

inclosing  suspensory  ligament  which  is  kept  stretched  by  its 
attachment  to  tlie  choroid.  When  the  ciliary  muscles  con- 
tract, the  choroid  is  pulled  forward  and  the  suspensory  liga- 
ment is  slackened,  thus  allowing  the  anterior  surface  of  the 
lens  to  bulge  outward. 

Proof  that  accommodation  is  accomplished  by  change  in 
curvature  of  the  anterior  surface  of  thedens. 

THE  MOVEMEXTS  OF  THE  PUPIL. 

The  pupil  is  contracted  when  light  falls  upon  the  retina, 
but  is  dilated  in  the  dark.  It  is  contracted  when  we  accom- 
modate for  near  objects,  but  it  is  dilated  when  we  accommo- 
date for  distant  ones.  It  is  contracted  when  the  optical  axes 
converge  and  dilated  when  they  become  i^arallel. 

The  contraction  of  the  pupil  is  an  active  movement ;  it  is 
not  certain  whether  dilation  of  the  pupil  is  due  to  the  condi- 
tion of  radial  muscle  fibres  or  to  simple  inhibition  of  the 
activity  of  the  circular  muscles. 

The  condition  of  the  eye  during  sleep. 

These  movements  of  the  pupil  are  the  result  of  reflex  and 
associated  actions.  When  the  movement  is  brought  about  by 
light  falling  upon  the  retina,  the  optic  nerve  is  the  afferent 

nerve  of  the  reflex  apparatus;  the  third  or  oculo-motor  nerve 
is  the  efferent  nerve  whose  excitement  causes  contraction,  and 

the  sj^mpathetic  is  the  eft'erent  dilator  nerve. 

There  is  union  between  the  reflex  centres  for  movement  of 
the  pupils;  for  subjecting  one  eye  to  changes  of  illumination 
produces  movement  of  tlie  opposite  pupil. 

The  action  of  drugs  upon  the  pupil,  as  of  atropin  or  physo- 
stigmin,  is  probably  wholly  local. 

ADYAXTAGES  AXD  DEFECTS   OF  THE  EYE  AS  AX  OPTI- 
CAL APPARATUS. 

Owing  to  its  accommodating  power  the  place  of  formation 
of  all  images  in  the  eye  is  at  the  principal  focus. 

The  theoretically  perfect  defining  power  of  the  eye  in  the 
region  of  the  fovea  centralis. 

IS 


—118— 

When  light  passes  through  a  spherical  lens  it  can  throw  a 
well  (lehned  image  of  larger  dimensions  upon  a  curved  sur- 
face, like  that  of  the  retina,  than  upon  a  plane  surface. 

The  special  defects  of  the  myopic,  hypermytropic  and  pres- 
byopic eye. 

The  s])herical  abcrrcdion  due  to  the  form  of  the  lens  is 
probably  insignihcant  in  comparison  with  other  optical  defects 
of  the  eye.  The  refractive  power  of  the  lens  varies  in  dif- 
ferent parts  of  it.  The  most  obvious  use  of  the  iris  is  to 
diminish  spherical  aberration  by  cutting  off  circumferential 
rays. 

The  refracting  surfaces  of  the  eye  are  not  perfect  sections 
of  a  sphere,  but  are  often  more  convex  along  one  meridian 
than  another.  Hence,  lines  having  different  directions  can- 
not all  be  brought  simultaneously  to  a  focus  on  the  retina. 
This  leads  to  a  defect  known  as  astigmatism..  Illustrations 
of  astigmatism. 

Methods  of  determining  the  cJiromatic  aherTation  of  the 
eye. 

Eutopic  phenomenon. — Floating  particles  in  the  vitreous 
humour,  the  musca'  volitantes.  Imperfections  in  the  lens. 
Tears  on  the  cornea.  The  observation  of  the  margin  of  the 
pupil.  The  luminosity  and  the  floating  colored  clouds  of 
the  retina. 

The  refracting  surfaces  of  the  eye  are  not  centred  on  the 
optic  axis. 

SENSATIONS  OF  VISION. 

The  education  of  the  senses. 

The  part  of  the  retina  which  is  directly  excited  by  light  is 
the  posterior  layer  of  rods  and  cones. 

The  optic  nerve  itself  is  unirritable  towards  light.  The 
blind  s])ot.  The  shadows  of  the  retinal  blood-vessels  seen  as 
Purldnje's  figures. 

The  amount  of  energy  contained  in  a  luminous  wave  may 
be  exceedingly  small. 


— llil  - 

The  movement  of  pigment  in  the  retinal  epithelium  under 
under  the  influence  of  Kg] it. 

The  retinal  pigments  ^\  liicli  are  altered  by  light. 

Bt)th  rods  and  cones  are  pi'obably  directly  irritated  b ;• 
light;  in  certain  animals  the  first  and  in  others  the  second  of 
these  elements  seems  to  be  absent.  It  has  been  conjf  ctured 
that  rods  serve  chiefly  to  give  mere  sensation  of  light,  while 
the  cones  are  adapted  to  permit  of  distinctness  of  vision. 

The  demcmstration  of  the  yellow  pigment  of  the  macula 
lutea. 

Perception  of  the  rods  and  cones  of  one's  own  retina. 

The  alternate  spontaneous  blindness  of  the  two  eyes. 

Temporary  blindness  produced  by  pressure  on  the  bulb. 

THE  RELATION  OF  THE  DURATION  AND  STRENGTH  OF 
THE  STIMULUS  TO  THE  SENSATION. 

Subjective  and  objective  light. 

The  sensation  produced  by  a  momentary  flash  of  light  has 
a  much  longer  duration  than  the  stimulus  itself;  when  single 
flashes  follow  each  other  sufficiently  rapidly  the  separate  sen- 
sations are  fused.  The  intervals  between  the  flashes  must  be 
smaller  the  stronger  the  light,  in  order  that  the  separate  sen- 
sations may  he  completely  fused.  The  duration  of  the  "after 
image"  is  longer  the  stronger  the  light  which  caused  the  sen- 
sation. 

"Positive"  tnd  "negative"  after-images. 

Instantaneous  photography.  Apparent  motion  produced 
by  the  fusion  of  sensations  from  momentary  stimuli. 

The  intensity  of  sensation  varies  with  the  intensity  of  illu- 
mination ;  but  the  relation  of  the  variation  of  the  intensities 
is  not  a  simple  one. 

Weber's  law.  The  increase  of  stimulus  which  is  necessary 
to  produce  the  smallest  increase  of  sensation  bears  always  the 
same  proportion  to  the  whole  intensity  of  the  stimulus  which 
has  already  been  applied.     Practical  application  of  this  law. 


—120— 

THE  DISTINCTION  AND  FUSION  OF  SIMULTANEOUS  SEN- 
SATIONS. 

Two  objects  appear  as  one  if  brought  near  enongli  together. 
In  order  to  appear  as  two  objects,  the  distance  between  their 
images  on  the  retina  must  not  be  less  than  the  diameter  of  a 
single  retina  cone.  In  the  human  eye  objects  thrown  thus 
near  together  in  the  fovea  of  the  retina  may  still  be  distin- 
guished apart.  Toward  the  periphery  of  the  retina  the  dis- 
tinction is  not  nearly  as  fine.  Green. and  blue  light,  in  the 
order  named,  each  permit  of  finer  definition  than  white  light, 
while  red  light  is  least  advantageous. 

Cause  of  the  broken  outline  of  fine  lines  which  are  drawn 
close  together. 

The  distinction  between  cerebral  and  retinal  visual  areas. 

The  number  of  cones  in  the  retina  is  much  greater  than  that 
of  the  fibres  in  the  optic  nerve. 

COLOR  SENSATIONS. 

Besides  the  sensations  of  white  and  black,  we  may  attain 
certain  sensations  of  color,  the  quality  of  each  of  which  is 
determined  by  the  wave  length  of  the  incident  light.  The 
spectral  colors  are  red,  orange,  yellow,  green,  blue,  violet. 
The  fusion  of  blue  and  red  produces  another  simple  color, 
purple,  not  found  in  the  spectrum.  The  physical  cause  of 
color. 

All  the  hues  of  nature  may  be  imitated  by  the  proper  fusion 
of  the  primary  color  sensations  with  each  other  or  with  white 
or  black. 

The  origin  of  browns,  and  olive-greens.  Various  methods 
and  the  resiilts  of  mixing  simple  color  sensations. 

The  cause  of  the  difference  between  the  sensation  obtained 
by  the  mixture  of  two  colors  on  the  retina  and  that  derived 
from  the  mixture  of  the  pigments  themselves. 

A  cplor  is  said  to  be  more  or  less  saturated  according  as 
it  contains  less  or  more  of  white  light.  No  color  is  abso- 
lutely saturated. 


—  121  - 

Every  color  which  is  suHicieiitly  ilhiiiiinated  appears  white. 

8timuhition  of  a  considerable  retinal  area  is  necessary  to 
excite  a  sensation  of  color;  very  small  colored  objects  appear 
black. 

Color  sensation  produced  by  electric  stimulation  of  the  eye. 

Gray  is  a  mixture  of  white  and  black. 

Complementary  colors  are  those  which,  when  mixed  on  the 
retina,  produce  the  sensation  of  white  light. 

The  following  are  comjjlementary  colors; — Red  and  green- 
blue;  orange  and  cyan-blue;  yellow  and  ultramarine-blue; 
greenish-yellow  and  violet;  green  and  purple. 

Any  three  colors,  situated  in  the  spectrum  as  far  apart  as 
possible,  may,  in  proper  proportions,  together  produce  white ; 
by  varying  the  proportions,  all  of  the  other  spectral  colors 
may  be  derived  from  the  three  primary  colors. 

The  Hcring  theory  of  color  sensation. 

The  Young-HelmhoJfz  theory  of  colour  sensation. 

The  difference  of  sensitiveness  of  the  retina  to  different 
colors.  In  a  waning  light  the  red  sensations  disappear  first 
and  the  blue  last;  hence,  red  objects  first  become  dark. 

COLORED  AFTER-IMAGES. 

The  sensation  of  light  lasting  longer  than  the  stimulus,  an 
object  may  still  be  seen  for  a  time  after  its  removal  from  the 
field  of  vision;  such  sensations  are  known  as  affo'-inuiges. 
The  after-image  is  at  first  positive,  or  of  the  same  brightness 
and  color  as  the  stimulus;  soon  it  becomes  negoHre,  or  of 
brightness  and  color  complementary  to  the  original  stimulus. 

Successive  Coufrasf.  The  greater  saturation  of  a  color  by 
contrast.  Colors  whose  infl^^ence  is  mutually  aiding  or  de- 
teriorating. 

The  conditions  of  the  retina  upon  which  depend  the  bright- 
ness or  darkness  of  an  after-image. 

Explanation  of  changes  in  after-images  as  a  result  of  re- 
tinal fatigue. 

The  successive  fading  of  the  colors  of  an  after-image. 

The  intrinsic  light  of  the  retina. 


—122— 
SIMULTANEOUS  CONTRAST. 

Light  aiul  dark  surfaces  appear  respectively  brighter  and 
darker  when  viewed  together.  The  phenomena  of  colored 
shadows.  When  a  piece  of  gray  paper  is  laid  on  a  colored 
ground  and  covered  with  tissue  paper,  the  gray  slip  aj^pears 
to  have  a  color  complementary  to  that  of  the  surface.  The 
comparison  of  strips  of  black  paper  respectively  seen  through 
and  reflected  by  colored  glass  plates. 

The  phenomena  of  simultaneous  contrast  occur  as  if  every 
colored  image  which  falls  upon  the  retina  rendered  the  neigh- 
boring parts  of  the  retina  more  irritable  toward  the  comple- 
mentary color. 

The  physiological  basis  of  taste  in  color. 

COLOR  BLINDNESS. 

Home  persons  are  incapable  of  acquiring  certain  color  sen- 
sations. The  most  common  form  of  the  defect  is  that  of  "red- 
blindness."  To  persons  suffering  from  it,  the  colors  rose-red 
and  bluish-green  are  identical.  They  distinguish  in  the  spec- 
trum but  two  colors,  calling  them  yellow  and  blue;  under  the 
yellow  they  include  the  red,  orange,  yellow  and  green,  and 
blue  and  violet  are  called  blue. 

About  5  p.  c.  of  the  population  are  affected  to  some  degree 
with  red-blindness. 

Temporary  color-blindness  induced  by  wearing  colored 
glasses,  and  by  the  ingestion  of  santonin. 

A  rarer  form  of  color-blindness  is  said  to  occur  in  which  the 
sensation  of  red  is  preserved,  but  that  of  green  is  lost. 

Color-blindness  on  the  periphery  of  the  retina.  Methods 
of  testing  for  color-blindness. 

A^ISUAL  PERCEPTIONS. 

The  mind  derives  ideas  from  simple  visual  sensations;  sen- 
sations give  rise  to  visual  perceptions. 

In  most  of  our  visual  ideas  we  take  little  account  of  simple 


—123— 

sensations,  but  use  directly  the  complex  jnch/menis  founded 
on  them. 

The  psychical  eifects  produced  by  viewin<2;  a  landscai)e 
through  differently  colored    gbisse.s. 

The  perception  of  the  positions  of  objects.  The  localiza- 
tion of  objects  by  vision  is  a  subjective  process.  The  images 
of  objects  are  inverted  on  the  retina. 

MODIFIED  PERCEPTIONS. 

Irradiation:  bright  objects  appear  larger  than  dark  ones  of 
the  same  size.     Illustrations. 

The  blind  spot  is  not  perceived  chiefly  because  no  sensation 
is  aroused  by  it. 

The  retina  itself  gives  rise  in  the  dark  to  luminous  sensa- 
tions. 

Intrinsic  colored  images  of  the  retina.  Lights  produced 
by  pressure  on  the  eyeball.  Effect  of  stimulating  the  eye  or 
optic  ner\'e. 

Visual  judgments  of  size.  The  only  method  of  determin- 
ing the  relative  size  of  objects  is  the  comparison  of  the  mag- 
nitude of  their  images  thrown  upon  the  retina ;  our  estimation 
of  their  real  size  depends  upon  the  distance  from  the  eye  at 
which  they  are  believed  to  be  situated.  This  distance  seems 
greater  when  sulidivided  by  intervening  objects  and  when 
seen  obscurely ;  the  apparent  size  of  the  moon  in  mid-sky  and 
on  the  horizon;  comparison  of  the  lengths  of  two  equal  lines, 
one  of  which  is  subdivided  and  the  other  not;  the  greater 
apparent  size  of  objects  in  a  fog.  The  appreciation  of  differ- 
ence of  size  by  contrast. 

Judgments  of  the  magnitude  of  angles. 

VISION  WITH  TWO  EYES. 

In  general,  the  reason  why  an  object  viewed  with  two  eyes 
appears  single  is  that  the  image  of  each  point  on  it  falls  upon 
"corresponding"  or  "identical"  areas  of  the  two  retinas. 
Points  on  the  inner  side  of  one  retina  have  their  correspond- 
ing points  on  homologous  parts  of  the  outer  side  of  the  other. 


—124— 
MOVEMENTS  OF  THE  EYEBALL. 

The  orbit  and  the  eyeball  form  a  ball  and  socket  joint,  the 
centre  of  rotation  being  1.8  mm.  behind  the  centre  of  the  eye. 

The  reflex  fixation  of  external  objects  which  keeps  the  eye- 
balls at  rest  when  the  head  is  moved. 

The  "primary"  and  "secondary"  positions  of  the  eye.  The 
position  of  the  resting  eye. 

The  rotation  of  the  eye  around  its  visual  axis  when  the 
latter  is  changed  from  a  primary  to  an  oblique  position. 

The  muscles  of  the  eyeball  and  the  movements  brought 
about  by  their  action. 

The  co-ordination  of  the  movements  of  the  eyeball.  The 
double  images  that  result  when  the  co-ordination  centre  fails 
to  act. 

Apparent  rotation  of  toothed  wheels  brought  about  by  the 
rinsing  motion. 

False  judgments  of  motion. 

THE  IIOEOPTER. 

Distinct  vision  of  objects  can  be  had  only  when  the  images 
of  their  parts  fall  upon  corresponding  points  of  the  two 
retinas.  In  any  given  position  of  the  visual  axes  such  corre- 
sponding points  are  projected  outward  upon  some  definite 
line  or  surface,  and  this  line  or  area  of  distinct  vision  is  known 
as  the  horopter.  The  horopter  changes  its  form  or  position 
with  changes  of  direction  of  the  visual  axes.  When  standing 
erect  and  looking  toward  the  horizon  the  horopter  is  upon  the 
ground  before  the  eyes.  The  precautions  necessary  in  walk- 
ing upon  a  hillside,  or  upon  a  level  while  looking  through  a 
prism. 

THE  JUDGMENTS  THAT  ARISE  FROM  BINOCULAR 
VISION. 

By  means  of  the  movements  of  the  two  eyeballs  and  the 
images  falling  upon  corresponding  point  of  the  two  retinas, 


—125— 

we  are  enabled  to  form  certain  judgments  concerning  the 
form,  size,  and  distance  of  objects. 

Illustrations  of  the  judgments  concerning  size  and  distance 
as  depending  on  the  "  muscular  sense  "  of  innervation  of  the 
eye-muscles. 

The  idea  of  perspective  aroused  by  the  shading  and  color- 
ing of  objects. 

When  a  solid  object  is  viewed  the  images  falling  upon  the 
two  retinas  cannot  be  identical;  they,  however,  do  not  give 
rise  to  double  vision,  but  are  fused  in  the  cerebrum  so  as  to 
give  the  perception  of  single  solid  objects.  The  shading  of 
an  object  largely  assists  in  the  formation  of  a  judgment  of  its 
solidity. 

Applications  of  the  stereoscope.     The  telestereoscope. 

The  psychical  influence  of  the  use  of  two  eyes. 

When  two  different  colors  or  white  and  black  are  viewed  at 
the  same  time,  each  by  one  eye,  there  is  not  a  fusion  of  color 
in  the  sensation  but  an  alternate  mastery  of  one  and  the 
other. 

DEMONSTRATIONS. 

Scheiner's  experiment.  Observation  of  the  movements  of 
the  pupil.  Astigmatism.  The  blind  spot.  Purkiuje's  figures. 
The  mixture  of  colors  upon  a  rotating  disk.  Complementary 
colors.  After-images.  Tests  for  color-blindness.  The  yellow 
spot.  Irradiation.  Simultaneous  contrast.  Judgments  of 
distance.  Judgments  of  motion.  The  stereoscope.  The 
telestereoscope. 


XX.    THE  EAR  AND  HEARING. 

THE  STRUCTURE  OF  THE  EAR. 

The  organ  of  hearing  may  be  considered  to  be  made  up  of 
three  parts;  -an  external  ear,  composed  of  the  pinna  and 
auditory  meatus,  the  latter  being  separated  by  the  tympanic 
membrane  from  the  middle  ear  or  tympanum.  The  tympanum 
contains  the  auditory  ossicles,  malleus,  incus  and  stapes,  and 
its  cavity  opens  upon  the  upper  wall  of  the  pharynx  by  means 
of  the  Eustachian  tube;  an  infernal  ear,  consisting  of  a 
membranous  labyrinth,  to  which  the  auditory  nerve  is  dis- 
tributed, which  is  contained  within  a  bony  labyrinth ;  the  two 
labyrinths  are  filled  with  fluid  known  respectively  as  the 
endolymph  and  the  peril ymj^h.  The  division  of  the  bony 
labyrinth  into  vestibule,  semi-circular  canals  and  cochlea. 
The  fenestra  rotunda  and  fenestra  oralis  are  placed  in  the 
bony  wall  separating  the  tympanum  respectively  from  the 
scala  tympani  of  the  cochlea,  and  from  the  vestibule.  The 
membranous  vestibule  is  composed  of  two  sacs,  the  saccule 
and  utricle,  whose  cavities  are  indirectly  united.  The  mem- 
branous semi-circular  canals  spring  from  the  utricle,  and  the 
cavity  of  the  saccule  is  continuous  with  that  of  the  mem- 
branous canal  of  the  cochlea.  The  auditory  hair-cells  upon 
the  maculse  of  the  vestibular  sacs  and  on  the  cristse  of  the 
ampullse  of  the  semi-circular  canals.  The  otoliths  within  the 
sacs  and  ampullae. 

The  microscopic  structure  of  the  membranous  cochlea  and 
of  the  organ  of  Corti  contained  in  it. 

THE  SPECIAL  FUNCTIONS    OF    THE    PARTS   OF  THE 

ACOUSTIC  APPARATUS. 

THE  PIXNA  OK  EXTERNAL  EAR. 

The  modification  of  the  concha  in  different  animals.  Its 
purpose  is  to  collect  the  waves  of  sound  from  the  external 
air. 


—128— 

The  use  of  the  pinna  by  animals  in  determining  the  direc- 
tion of  sound. 

THE  MEMBRAI^A  TYMPAiq"!. 

The  curved  surface  and  funnel-shape  of  the  tympanic 
membrane.  This  membrane  is  easily  set  vibrating  by  air 
waves,  and  has  no  fundamental  note  of  its  own.  Its  peculiar 
shape  adapts  it  for  transmitting  motions  of  great  amplitude 
and  small  energy  as  motions  of  small  amplitude  and  great 
energy. 

The  movements  of  the  auditory  ossicles.  The  ossicles 
form  a  sort  of  compound  lever  by  which  the  oscillations  of 
the  tympanic  membrane  are  exactly  transferred  to  the  mem- 
brane of  the  fenestra  ovalis,  but  with  diminished  amplitude 
and  correspondingly  increased  force. 

The  mean  extent  of  the  excursions  of  the  tip  of  the  malleus 
is  probably  near  1-28  mm.  The  excursions  of  the  stapes  are 
only  f  as  great,  but  are  1^  times  as  energetic. 

The  tensor  tympani  muscle  serves  by  its  contraction  to  pre- 
vent the  tympanic  membrane  being  pushed  out  too  far. 

The  laxator  tympani  muscle  probably  by  its  contraction 
causes  the  ear-drum  to  move  outward. 

The  stapedius  muscle  probably  acts  to  prevent  the  stapes 
being  driven  too  far  into  the  fenestra  ovale. 

THE  EUSTACHIAN  TUBE. 

This  channel  connecting  the  middle  ear  and  the  pharynx 
serves  to  keep  the  pressure  within  the  tympanic  cavity  equal 
to  that  of  the  atmosphere.  The  tube  is  probably  only  opened 
during  the  act  of  swallowing. 

THE  GENERATION  OF  AUDITORY  SENSATIONS. 

THE  MEMBEANOUS  LABYRINTH. 

The  filaments  of  the  auditory  nerve  end  in  the  maculae  and 
cristse  of  the  internal  ear  and  in  the  basilar  membrane  of  the 
cochlea.     It  is  supposed  that  vibrations  of  the  endolymph  set 


—129— 

these  end-organs  in  corresponding  motion,  tlius  mechanically 
stimulating  the  auditory  nerve. 

The  distinction  between  physical  and  physiological  sound. 
Graphic  representaticm  of  air  waves. 

The  transmission  of  sound  through  the  bones  of  the  skull ; 
hearing  without  a  tympanic  membrane. 

Sounds  may  be  divided  into  musical  tones  which  are  caused 
by  rhythmic  or  periodic  vibrations  of  the  air,  and  noises 
which  are  due  to  non-periodic  vibrations. 

Sounds  are  distinguished  by  the  three  characters  of  loud- 
ness, pitch  and  qiialitij.  The  physical  peculiarities  implied 
in  these  terms. 

The  physical  range  of  audible  tones. 

Each  musical  note  is  made  up  of  a  fundamental  tone,  which 
determines  the  pitch,  with  which  a  greater  or  less  number  of 
overtones  are  combined,  the  latter  determining  the  quality  of 
the  note. 

The  manner  in  which  the  partial  tones  are  produced 
together  with  the  fundamental  tone.  It  is  the  varied  predom- 
inance of  different  partials  which  causes  the  dift'erence  of 
quality  in  the  notes  of  various  musical  instruments. 

The  composite  air-waves  formed  by  the  fusion  of  partial 
vibrations.     . 

Nearly  every  body  capable  of  periodic  vibration  has  a  fun- 
damental tone  of  its  own.  The  tympanic  membrane  has  no 
particular  fundamental  tone. 

The  simple  arithmetical  relations  of  the  vibration  rates  of 
the  tones  of  a  musical  chord. 

The  production  of  musical  tones  and  notes  upon  the  siren. 

Sympathetic  vibrations.  The  analysis  and  synthesis  of 
musical  tones. 

The  high  fundamental  tone  of  the  external  auditory  meatus. 

There  is  reason  to  think  that  the  organ  of  Corti  may  be 
regarded  as  a  musical  instrument  capable  of  responding  by 
sympathetic  vibration  to  all  audible  tones. 

The  physiological  basis  of  the  musical  sense. 


—1  Bo- 
lt has  been  supposed  that  the  auditory  hairs  upon,  and  the 
otoliths  near,  the  macula?  and  crist?e  of  the  labyrinth  are  con- 
cerned in  the  reproduction  of  irregular  vibrations  known  as 
noises. 

The  simplest  aural  apparatus  known  is  a  mere  sac  whose 
walls  are  set  with  hair-cells,  and  whose  cavity  is  filled  with 
fluid  containing  otoliths. 

When  single  sounds  are  repeated  with  sufficient  rapidity, 
they  fuse  into  a  continuous  tone  whose  pitch  is  determined  by 
the  rate  at  which  the  single  sounds  succeed  each  other. 

Tones  produced  by  vibrations  recurring  less  than  30  times 
a  second  are  not  heard.  The  upper  limit  of  auditory  sensation 
is  reached  when  vibrations  recur  38,000  times  per  second. 
The  variation  of  this  limit  with  the  loudness  of  sound  and 
with  the  individual. 

The  power  of  distinguishing  pitch  differs  much  in  different 
parts  of  the  scale.  The  fineness  of  musical  appreciation  of 
quality  and  pitch. 

The  subjective  nature  of  sound.  Individual  differences  in 
the  appreciation  of  tones. 

AUDITORY  JUDGMENTS. 

Any  stimulation  of  the  auditory  nervous  apparatus  is  inter- 
preted as  dae  to  sound  waves. 

From  the  loudness,  quality,  and  pitch  of  sounds,  we  for  m 
judgments  as  to  their  origin,  direction  and  distance.  The 
nature  of  ventriloquism. 


XXI.    THE  ORGAN  AND  SENSE  OF  SMELL. 

The  cavity  of  the  nose  on  each  side  of  the  nasal  septum  is 
divided  functionally  into  a  lower  respiratory  and  upper  olfac- 
tory chamber.  The  olfactory  mucous  membrane,  to  which 
the  olfactory  nerve  is  distributed,  lines  the  upper  and  middle 
turbinated  parts  of  the  fossae  and  the  upper  part  of  the  sep- 
tum. The  ciliated  epithelium  and  mucous  glands  of  the 
respiratory  chambers  of  the  nose. 

The  termination  of  the  nerve  fibres  in  the  olfactory  cells  of 
the  upper  chamber. 

THE  ORIGIN  OF  SENSATIONS  OF  SMELL. 

Odorous  particles  are  carried  by  diffusion  into  the  olfactory 
chamber  of  the  nose,  or  drawn  into  it  by  active  inhalation. 

Odorous  bodies  must  come  into  contact  with  the  olfactory 
mucous  membrane  in  order  to  produce  a  sensation,  and  the 
particles  must  not  be  in  liquid  form.  Filling  the  nose  with 
an  odorous  liquid  causes  no  sensation  of  smell.  "When  sev*- 
eral  odors  are  simultaneously  inhaled,  the  peculiarity  of  each 
may  be  distinguished. 

Localization  of  an  odor  by  the  sense  of  smell  is  very  im- 
perfect. 

The  sensation  requires  some  time  to  develop  itself  after 
application  of  the  stimulus,  and  may  last  for  a  considerable 
time. 

Certain  pungent  substances,  as  ammonia,  give  rise  to  sensa- 
tions through  the  nose  which  are  not  those  of  smell  proper; 
are  probably  due  to  stimulation  of  the  fifth  nerve.  There 
may  be  sensations  of  smell  of  purely  subjective  origin. 


XXII.    THE  ORGAN  AND  SENSE  OF  TASTE. 

The  glossopharyngeal  and  the  lingual  nerves  are  the  special 
nerves  of  taste. 

The  modified  termination  of  the  gustatory  nerves  in  the 
mucous  membrane  of  the  tongue  and  palate. 

Many  sensations  which  we  are  accustomed  to  distinguish  as 
those  of  taste  are  really  sensations  of  smell. 

Sapid  substances  may  be  classified  as  sweet,  sour,  saline 
and  bitter.     They  act  in  solution  as  chemical  stimuli. 

Sensations  of  taste  may  arise  from  mechanical  or  electrical 
stimulation  of  the  gustatory  apparatus. 


XXIII.    GENERAL  SENSIBILITY  AND  SENSATIONS  OF  TOUCH. 

The  distribution  and  modified  terminations  of  sensory 
nerves. 

We  possess  a  certain  faculty  of  general  sensibility  which 
gives  rise  to  a  consciousness  of  irritation  in  the  body  without 
enabling  us  to  localize  the  stimulus  or  distinguish  its  nature. 
Such  are  the  sensations  due  to  irritation  of  a  nerve  trunk  or 
of  the  viscera.  Such  sensations  readily  merge  into  those  of 
pain. 

The  more  special  sensations  of  feeling  are  those  derived 
from  touch,  temperature  and  muscular  activity. 

TACTILE  SENSATIONS. 

SENSATIONS  OF  PRESSURE. 

The  smallest  difference  which  can  be  distinguished  between 
two  unequal  weights  laid  upon  the  skin  is  proportional  to  the 
magnitude  of  the  weights. 

When  separate  sensations  of  contact  succeed  each  other 
with  sufficient  rapidity  they  become  fused. 

Not  all  parts  of  the  skin  are  equally  sensible  to  variations 
or  pressure. 

Sensations  of  contact  are  present  when  the  intensity  of  the 
pressure  is  varied,  and  fade  away  when  it  becomes  constant. 

A  cold  body  is  judged  to  be  heavier  than  a  warm  one  of 
equal  weight. 

There  is  reason  to  believe  that  there  exist  tactual  nerves 
distinct  from  those  of  general  sensibility. 

TACTILE  PERCEPTIONS  AND  JUDGMENTS. 

Sensations  of  contact  are  referred  generally  to  definite 
localities  on  the  skin.     The  erroneous  judgments  that  arise 


—  13fi— 

from  the  irritation  of  the  nerves  of  an  amputated  limb. 
Mistaken  judgments  arising  when  a  marble  is  rolled  between 
the  tips  of  two  crossed  fingers. 

The  power  localizing  contact  upon  the  skin  is  not  the  same 
in  all  parts.     The  division  of  the  skin  into  tactual  areas. 

The  power  of  localization  is  most  marked  upon  the  tip  of 
the  tongue  and  the  palmar  surface  of  the  finger,  and  least 
marked  upon  the  forearm,  sternum,  and  back. 

The  fineness  of  tactile  perception  is  greatly  increased  by- 
exercise. 

THE  TEMPERATURE  SENSE. 

Bodies  warmer  or  colder  than  the  skin  when  in  contact  with 
it  give  rise  to  sensations  of  heat  or  cold.  The  erroneous  judg- 
ments that  may  arise  from  artificially  rendering  the  two  hands 
of  different  temperatures. 

The  range  of  finest  distinction  of  temperature  is  included 
between  limits  which  lie  near  the  body  temperature. 

Not  all  parts  are  equally  sensitive  to  variations  of  tempera- 
ture. 

There  are  probably  special  afferent  temperature  nerves 
which  are  irritated  by  variations  of  temperature. 

There  is  reason  to  believe  that  the  sensation  of  heat,  cold, 
and  pressure,  respectively,  are  aroused  through  the  excitement 
of  different  sensory  nerves. 

THE  MUSCULAR  SENSE. 

We  commonly  estimate  the  weight  *of  bodies  by  observing 
the  intensity  of  muscular  exertion  necessary  to  lift  them. 

Muscular  sensations  are  probably  peripheral  in  origin. 

The  effects  following  diminution  of  tactile  and  muscular 
sensibility  in  locomotor  ataocy. 

Judgments  which  arise  from  the  muscular  sense. 


INDEX. 

PAGE. 

I.— The  object  of  physiology  and  the  functions  of  living  matter 5 

II.— The  nature  of  physiological  laws 6 

III.— The  lymph  and  blood 7 

Coagulation  of  blood 8 

Causes  of  coagulation 8 

Chemistry  of  "blood 10 

History  of  blood  corpuscles 10 

IV.— The  chemistry  of  animal  tissues 11 

Proteids 12 

Fats  and  carbohydrates 13 

Physiological  metabolites 14 

v.— Epii helium,  connective  tissue  and  the  skeleton 15 

Joints  and  bony  levers •. 17 

VI.— The  contractile  tissues 18 

Ciliated  cells  and  classification  of  muscle 18 

Electrical  phenomena 23 

Chemistry  of  muscle 24 

Physiology  of  unstriated  muscle 26 

VII.— Nervous  tissues 27 

Histology  of  nerves 27 

Classification  and  physiology  of  nerves 28 

Electrotonus ; 29 

viii.— Reflex  action 30 

Inhibition 32 

IX.— The  circulation  of  the  blood , 35 

Structure  of  the  organs  of  circulation 35 

Physiology  of  the  heart 37 

Hydraulics  of  the  circulation 44 

Vaso-motor  regulation 47 

Circulation  of  lymph 49 

X.— The  respiration 53 

Structure  of  the  organs,  and  the  movements  of  respiration 53 

Capacity  of  the  lungs,  and  changes  of  air  iniespiration. 55 

Changes  of  the  blood  in  the  lungs 56 

Nerves  of  respiration  and  action  of  the  respiratory  centre 57 

XL— The  skin  and  its  appendages 61 

xn. — The  kidneys  and  their  secretion 63 

xni. — Physiology  of  secretion 67 

XIV. — Foods  and  force-regulators 71 

XV. — Digestion 73 

The  saliva 73 

Deglutition ■: 74 

The  stomach  and  gastric  juice 75 

Changes  of  food  in  the  intestine 79 

XVI.— Nutrition 87 

The  liver  and  the  history  of  glycogen 88 

Diabetes  and  fat-formation 89 

The  spleen,  and  the  origin  of  urea .' 91 

Animal  heat 95 

XVII.— The  spinal  cord 99 

The  cord  as  a  reflex  centre 100 

Paths  of  conduction  in  the  cord 101 

XVIII.— The  brain 105 

Changes  produced  in  ananimal  by  extirpation  of  the  cerebrum 105 

Localization  of  function  in  the  cerebrum 106 

('orpora  striata,  optic  thalami  and  corpora  quadrigemiua 108 

The  cerebellum. .r 109 

The  semicircular  canals  and  equilibrium 110 

XIX. — The  eye  and  sight 113 

The  eye  as  an  optical  instrument 114 

Accommodatii  n 116 

Movements  of  the  pupil - 117 

"Visual  sensations 118 

Color  sensations 120 

Visual  perctptions 122 

XX.— The  ear  and  hearing 127 

Functions  of  the  component  parts  of  the  ear 127 

Auditory  sensations 128 

XXI. — Theorgan  and  sense  of  smell 131 

XXII.— The  organ  and  sense  of  taste 133 

xxni.— Sensations  from  the  skin 135 

General  sensation 135 

The  muscular  sense 136 


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